Resin, resist composition and method for producing resist pattern

ABSTRACT

wherein Ra8 represents an alkyl group which may have a halogen atom, a hydrogen atom or a halogen atom; Za1 represents a single bond or *—(CH2)n3—CO-L54-; h3 represents an integer of 1 to 4; L51, L52, L53 and L54 each independently represent —O— or —S—; s1 represents an integer of 1 to 3; s1′ represents an integer of 0 to 3; R1 represents a hydrogen atom or a methyl group; A1 represents a single bond or *—CO—O—; R2 represents a halogen atom, a hydroxy group, a haloalkyl group or an alkyl group; mi represents an integer of 1 to 3; and ni represents an integer of 0 to 4, in which mi+ni≤5.

TECHNICAL FIELD

The present invention relates to a resin, a resist composition., and amethod for producing a resist pattern using the resist composition andthe like.

BACKGROUND ART

Patent Document 1 mentions a resist composition comprising a resinincluding the following structural units.

Patent Document 2 mentions a resist composition comprising a resinincluding the following structural units.

Patent Document 3 mentions a resist composition. comprising a resinincluding the following structural units.

Patent Document 4 mentions a resist composition comprising a resinincluding the following structural units.

PRIOR ART DOCUMENT Patent Document

Patent Document 1: JP H08-101507 A

Patent Document 2: JP 2014-041327 A

Patent Document 3: JP 2002-214788 A

Patent Document 4: JP 2013-205811 A

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

An object of the present invention is to provide a resin which forms aresist pattern with CD uniformity (CDU) better than that of a resistpattern formed by a resist composition comprising the above-mentionedresin.

Means for Solving the Problems

The present invention includes the following inventions.

-   [1] A resin comprising a structural unit represented by formula    (a1-5) and a structural unit represented by formula (I):

wherein, in formula (a1-5).

-   -   P^(a8) represents as alkyl group having 1 to 6 carbon atoms        which may have a halogen atom, a hydrogen atom or a halogen        atom,    -   Z^(a1) represents a single bond or *—(CH₂)_(h 3)—CO-L⁵⁴-, h3        represents an integer of 1 to 4, and represents a bonding site        to L⁵¹,    -   L⁵¹, L⁵², L⁵³ and L⁵⁴ each independently represent —O— or —S—,    -   s1 represents an integer of 1 to 3, and    -   s1′ represents an integer of 0 to 3:

wherein, in formula (I).

-   -   R¹ represents a hydrogen atom or a methyl group,    -   A¹ represents a single bond or *—CO—O—, and represents a bonding        site to carbon atoms to which —R¹ is bonded,    -   R² represents a halogen atom, a hydroxy group, a haloalkyl group        having 1 to 4 carbon atoms or an alkyl group having 1 to 12        carbon atoms, and —CH₂— included in the alkyl group may be        replaced by —O— or —CO—,    -   mi represents an integer of 1 to 3, and    -   ni represents an integer of 0 to 4, and when ni is 2 or more, a        plurality of R² may be the same or different from each other, in        which mi+ni≤5.

-   [2] The resin according to [1], further comprising at least one    structural unit selected from the group consisting of a structural    unit represented by formula (a1-1) and a structural unit represented    by formula (a1-2):

wherein, in formula (a1-1) and formula (a1-2).

-   -   L^(a1) and L^(a2) each independently represent —O— or        *—O—(CH₂)_(k1)—CO—O—, k1 represents an integer of 1 to 7, and *        represents a bonding site to —CO—,

R^(a4) and R^(a5) each independently represent a hydrogen atom or amethyl group,

R^(a6) and R^(a7) each independently represent an alkyl group having 1to 8 carbon atoms, an alicyclic hydrocarbon group having 3 to 18 carbonatoms, or a group obtained by combining these groups,

-   -   m1 represents an integer of 0 to 14,    -   n1 represents an integer of 0 to 10, and    -   n1′ represents an integer of 0 to 3.

-   [3] The resin according to [1] or [2], further comprising a    structural unit represented by formula (a2-A):

wherein, in formula (a2-A).

-   -   R^(a50) represents a hydrogen atom, a halogen atom or an alkyl        group having 1 to 6 carbon atoms which may have a halogen atom,    -   R^(a51) represents a halogen atom, a hydroxy group, an alkyl        group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6        carbon atoms, an alkylcarbonyl group having 2 to 4 carbon atoms,        an alkylcarbonyloxy group having 2 to 4 carbon atoms, an        acryloyloxy group or a methacryloyloxy group,    -   A^(a50) represents a single bond or        *—X^(a51)-(A^(a52)X^(a52))_(nb)-, and represents a bonding site        to carbon atoms to which —R^(a50) is bonded,    -   A^(a52) represents an alkanediyl group having 1 to 6 carbon        atoms,    -   X^(a51) and X^(a52) each independently represent —O—, —CO—O— or        —O—CO—,    -   nb represents 0 or 1, and    -   mb represents an integer of 0 to 4 and when mb is an integer of        2 or more, a plurality of R^(a51) may be the same or different        from each other.

-   [4] The resin according to any one of [1] to [3] , wherein A¹ is a    single bond.

-   [5] A resist composition comprising the resin according to any one    of [1] to [4] and an acid generator.

-   [6] The resist composition according to [5], wherein the acid    generator comprises a salt represented by formula (B1):

wherein, in formula (B1),

-   -   Q^(b1) and Q^(b2) each independently represent a fluorine atom        or a perfluoroalkyl group having 1 to 6 carbon atoms,    -   L^(b1) represents a divalent saturated hydrocarbon group having        1 to 24 carbon atoms, —CH₂— included in the divalent saturated        hydrocarbon group may be replaced by —O— or —CO—, and a hydrogen        atom included in the divalent saturated hydrocarbon group may be        substituted with a fluorine atom or a hydroxy group,    -   Y represents a methyl group which may have a substituent or an        alicyclic hydrocarbon group having 3 to 18 carbon atoms which        may have a substituent, and —CH₂— included in the alicyclic        hydrocarbon group may be replaced by —O—, —S(O)₂— or —CO—, and    -   Z represents an organic cation.

-   [7] The resist composition according to [5] or [6], further    comprising a salt generating an acid having an acidity lower than    that of an acid generated from the acid generator.

-   [8] A method for producing a resist pattern, which comprises:    -   (1) a step of applying the resist composition according to any        one of [5] to [7] on a substrate,    -   (2) a step of drying the applied composition to form a        composition layer,    -   (3) a step of exposing the composition layer,    -   (4) a step of heating the exposed composition layer, and    -   (5) a step of developing the heated composition layer.

Effects of the invention

By using a resist composition comprising a resin of the presentinvention, it is possible to produce a resist pattern with satisfactoryCD uniformity (CDU).

MODE FOR CARRYING OUT THE INVENTION

As used herein, “(meth)acrylate” means “at least one selected from thegroup consisting of acrylate and methacrylate” unless otherwisespecified. Descriptions such as “(meth)acrylic acid” and“(meth)acryloyl” also have the same meanings. When a structural unithaving “CH₂═C(CH₃)—CO—” or “CH₂═CH—CO—” is exemplified, a structuralunit having both groups shall be similarly exemplified. In groupsmentioned in the present description, those capable of having bothlinear and branched structures may have either a linear or branchedstructure. “Combined group” means a group obtained by bonding two ormore exemplified groups, and a valence of the group may appropriatelyvary depending on the bonding state. When stereoisomers exist, allstereoisomers are included.

As used herein, “solid component of the resist composition” means thetotal amount of components in which the below-mentioned solvent (E) isremoved from the total amount of the resist composition.

[Resin]

The resin of the present invention is a resin (hereinafter sometimesreferred to as “resin (A)”) including a structural unit represented byformula (a1-5) (hereinafter sometimes referred to as structural unit(a1-5)) and a structural unit represented by formula (I) (hereinaftersometimes referred to as structural unit (I)).

<Structural Unit (a1-5)>

Examples of the halogen atom include a fluorine atom, a chlorine atom, abromine atom and an iodine atom, and a fluorine atom is preferable.

Examples of the alkyl group having 1 to 6 carbon atoms which may have ahalogen atom include a methyl group, an ethyl group, a propyl group, abutyl group, a pentyl group, a hexyl group, a chloromethyl group, abromomethyl group, a fluoromethyl group, a difluoromethyl group, atrifluoromethyl group, a perfluoroethyl group, a perfluoropropyl group,a perfluorobutyl group, a perfluoropentyl group, a perfluorohexyl groupand the like.

In formula (a1-5) , R^(a8) is preferably a hydrogen atom, a methyl groupor a trifluoromethyl group.

L⁵¹ is preferably —O—.

Of L⁵² and L⁵³, one is preferably —O— and the other one is preferably—S—, L⁵² is more preferably —S—, and L⁵³ is more preferably —O—.

s1 is preferably 1 or 2, and more preferably 1.

s1′ is preferably an integer of 0 to 2, and more preferably 1.

L⁵⁴ is preferably —O—.

h3 is preferably 1 or 2, and more preferably 1.

Z^(a1) is preferably a single bond or *—CH₂—CO—O—.

Examples of the structural unit (a1-5) include structural units derivedfrom the monomers mentioned in JP 2010-61117 A. Of these structuralunits, structural units each represented by formula (a1-5-1) to formula(a1-5-6) are preferable, and a structural unit represented by formula(a1-5-1) or formula (a1-5-2) is more preferable.

When the resin includes the structural unit (a1-5), the content ispreferably 1 to 80 mol %, more preferably 10 to 75 mol %, still morepreferably 15 to 75 mol %, and yet more preferably 20 to 75 mol %, basedon all structural units of the resin (A).

<Structural Unit (I)>

In formula (I), R¹ is preferably a hydrogen atom.

Examples of the halogen atom for R² include a fluorine atom, a chlorineatom, a bromine atom and an iodine atom.

The haloalkyl group having 1 to 4 carbon atoms in R² represents an alkylgroup having 1 to 4 carbon atoms which has a halogen atom, and examplesthereof include a chloromethyl group, a bromomethyl group, afluoromethyl group, a difluoromethyl group, a trifluoromethyl group, aperfluorobutyl and the like.

Examples of the alkyl group having 1 to 12 carbon atoms for R² includealkyl groups such as a methyl group, an ethyl group, a propyl group, anisopropyl group, a butyl group, an isobutyl group, a tert-butyl group, apentyl group, a hexyl group, an octyl group and a nonyl group. Thenumber of carbon atoms of the alkyl group is preferably 1 to 9, and morepreferably 1 to 4.

When —CH₂— included in the alkyl group represented by R² is replaced by—O— or —CO—, the number of carbon atoms before replacement is taken asthe total number of carbon atoms of the alkyl group. R² may have ahydroxy group (a group in which —CH₂— included in a methyl group isreplaced by —O—) , a carboxyl group (a group in which —CH₂—CH₂— includedin an ethyl group is replaced by —O—CO—), an alkoxy group having 1 to 11carbon atoms (a group in which —CH₂— included in an alkyl group having 2to 12 carbon atoms is replaced by —O—), an alkoxycarbonyl group having 2to 11 carbon atoms (a group in which —CH₂—CH— included in an alkyl grouphaving 3 to 12 carbon atoms is replaced by —O—CO—), an alkylcarbonylgroup having 2 to 12 carbon atoms (a group in which —CH₂— included in analkyl group having 2 to 12 carbon atoms is replaced by —CO—) or analkylcarbonyloxy group having 2 to 11 carbon atoms (a group in which—CH₂—CH₂— included in an alkyl group having 3 to 12 carbon atoms isreplaced by —CO—O—).

Examples of the alkoxy group having 1 to 11 carbon atoms include amethoxy group, an ethoxy group, a propoxy group, a butoxy group, apentyloxy group, a hexyloxy group, an octyloxy group, a 2-ethylhexyloxygroup, a nonyloxy group, a decyloxy group, an undecyloxy group and thelike.

Examples of the alkoxycarbonyl group having 2 to 11 carbon atoms includea methoxycarbonyl group, an ethoxycarbonyl group, a butoxycarbonyl groupand the like, examples of the alkylcarbonyl group having 2 to 12 carbonatoms include an acetyl group, a propionyl group and a butyryl group,and examples of the alkylcarbonyloxy group having 2 to 11 carbon atomsinclude an acetyloxy group, a propionyloxy group, a butyryloxy group andthe like.

Of these, R² is preferably a halogen atom, a haloalkyl group having 1 to4 carbon atoms or an alkyl group having 1 to 12 carbon atoms (—CH₂—included in the alkyl group may be replaced by —O— or —CO—), and morepreferably a fluorine atom, a haloalkyl group having 1 to 3 carbon atomsor an alkyl group having 1 to 6 carbon atoms (—CH₂— included in thealkyl group may be replaced by —O— or —CO—).

mi is preferably1 or 2.

ni is preferably an integer of 0 to 2, and more preferably 0.

Examples of the structural unit (I) include structural units mentionedbelow. It is possible to exemplify structural units in which a hydrogenatom corresponding to R¹ is substituted with a methyl group instructural units represented by formula (I-1) to formula (I-8) andstructural units in which a methyl group corresponding to R¹ issubstituted with a hydrogen atom in structural units represented byformula (I-9) to formula (I-16) as specific examples of the structuralunit (I). Of these, structural units represented by formula (I-1) toformula (I-8) are preferable, structural units represented by formula(I-1) to formula (1-4) are more preferable, and a structural unitrepresented by formula (I-1) is still more preferable.

The content of the structural unit (I) in the resin (A) is preferably 3to 90 mol %, more preferably 5 to 85 mol %, still more preferably 5 to80 mol %, and yet more preferably 5 to 75 mol % based on all structuralunits.

The resin (A) of the present invention may be a polymer including one ormore structural units other than the structural unit (a1-5) and thestructural unit (I). Examples of the structural unit other than thestructural unit (a1-5) and the structural unit (I) include a structuralunit having an acid-labile group other than the structural unit (a1-5)(hereinafter sometimes referred to as “structural unit (a1)”), astructural unit which is a structural unit other than the structuralunit having an acid-labile group and has a halogen atom (hereinaftersometimes referred to as “structural unit (a4)”), a structural unithaving no acid-labile group other than the structural unit (I)(hereinafter sometimes referred to as “structural unit (s)”), astructural unit having a non-leaving hydrocarbon group (hereinaftersometimes referred to as “structural unit (a5)”) and the like. The“acid-labile group” means a group having a leaving group which iseliminated by contact with an acid, thus forming a hydrophilic group(e.g. a hydroxy group or a carboxy group). Particularly, the resin (A)preferably includes, in addition to the structural unit (a1-5), astructural unit having an acid-labile group, and more preferablyincludes at least one structural unit selected from the group consistingof a structural unit represented by formula (a1-1) and a structural unitrepresented by formula (a1-2). The resin (A) preferably includes, inaddition to the structural unit (I), a structural unit having noacid-labile group, and more preferably includes a structural unitrepresented by formula (a2-1).

<Structural Unit (a1)>

The structural unit (a1) is derived from a monomer having an acid-labilegroup (hereinafter sometimes referred. to as “monomer (a1)”).

The acid-labile group contained in the resin (A) is preferably a grouprepresented by formula (1) (hereinafter also referred to as group (1))and/or a group represented by formula (2) (hereinafter also referred toas group (2)):

wherein, in formula (1) R^(a1), R^(a2) and R^(a3) each independentlyrepresent an alkyl group having 1 to 8 carbon atoms, an alicyclichydrocarbon group having 3 to 20 carbon atoms or groups obtained bycombining these groups, or R^(a1) and R^(a2) are bonded each other toform an alicyclic hydrocarbon group having 3 to 20 carbon atoms togetherwith carbon atoms to which R^(a1) and R^(a2) are bonded,

ma and na each independently represent 0 or 1, and at least one of maand na represents 1, and

-   -   * represents a bonding site:

wherein, in formula (2), R^(a1′) and R^(a2)′ each independentlyrepresent a hydrogen atom or a hydrocarbon group having 1 to 12 carbonatoms, R^(a3)′ represents a hydrocarbon group having 1 to 20 carbonatoms, or R^(a2)′ and R^(a3)′ are bonded each other to form aheterocyclic ring group having 3 to 20 carbon atoms together with carbonatoms and to which R^(a2)′ and R^(a3)′ are bonded, and —CH₂— included inthe hydrocarbon group and the heterocyclic ring group may be replaced by—O— or —S—,

X represents an oxygen atom or a sulfur atom,

na′ represents 0 or 1, and

* represents a bonding site.

Examples of the alkyl group in R^(a1), R^(a2) and R^(a3) include amethyl group, an ethyl group, a propyl group, a butyl group, a pentylgroup, a hexyl group, a heptyl group, an octyl group and the like.

The alicyclic hydrocarbon group in R^(a1), R^(a2) and R^(a3) may beeither monocyclic or polycyclic. Examples of the monocyclic alicyclichydrocarbon group include cycloalkyl groups such as a cyclopentyl group,a cyclohexyl group, a cycloheptyl group and a cyclooctyl group. Examplesof the polycyclic alicyclic hydrocarbon group include adecahydronaphthyl group, an adamantyl group, a norbornyl group and thefollowing groups (* represents a bonding site). The number of carbonatoms of the alicyclic hydrocarbon group for R^(a1), R^(a2) and R^(a3)is preferably 3 to 16.

The group obtained by combining an alkyl group with an alicyclichydrocarbon group includes, for example, a methylcyclohexyl group, adimethylcyolohexyl group, a methylnorbornyl group, a cyclohexylmethylgroup, an adamantylmethyl group, an adamantyldimethyl group, anorbornylethyl group and the like.

Preferably, ma is 0 and na is 1.

When R^(a1) and R^(a2) are bonded each other to form an alicyclichydrocarbon group, examples of —C(R^(a1))(R^(a2))(R^(a3)) include thefollowing groups. The alicylic hydrocarbon group preferably has 3 to 12carbon atoms. * represents a bonding site to —O—.

Examples of the hydrocarbon group in R^(a1)′, R^(a2)′ and R^(a3)′include an alkyl group, an alicyclic hydrocarbon group, an aromatichydrocarbon group and groups obtained by combining these groups.

Examples of the alkyl group and the alicyclic hydrocarbon group includethose which are the same as mentioned in R^(a1), R^(a2) and R^(a3).

Examples of the aromatic hydrocarbon group include aryl groups such as aphenyl group, a naphthyl group, an anthryl group, a biphenyl group and aphenanthryl group.

Examples of the combined group include a group obtained by combining theabove-mentioned alkyl group and alicyclic hydrocarbon group (e.g., acycloalkylalkyl group), an aralkyl group such as a benzyl group, anaromatic hydrocarbon group having an alkyl group (p-methylphenyl group,a p-tert-butylphenyl group, a tolyl group, a xylyl group, a cumenylgroup, a mesityl group, a 2,6-diethylphenyl group, a2-methyl-6-ethylphenyl group, etc.), an aromatic hydrocarbon grouphaving an alicyclic hydrocarbon group (a p-cyclohexylphenyl group, ap-adamantylphenyl group, etc.), an aryl-cycloalkyl group such as aphenylcyclohexyl group, and the like.

When R^(a2)′ and R^(a3)′ are bonded each other to form a heterocyclicring together with carbon atoms and X to which R^(a2)′ and R^(a3)′ arebonded, examples of —C(R^(a1)′) (R^(a2)′)—X—R^(a3)′ include thefollowing groups. * represents a bond.

Of R^(a1)′ and R^(a2)′, at least one is preferably a hydrogen atom.

na′ is preferably 0.

Examples of the group (1) include the following groups.

A group wherein, in formula (1), R^(a1), R^(a2) and R^(a3) are alkylgroups, ma=0 and na=1. The group is preferably a tert-butoxycarbonylgroup.

A group wherein, in formula (1), R^(a1) and R^(a2) are bonded each otherto form an adamantyl group together with carbon atoms to which R^(a1)and R^(a2) are bonded, R^(a3) is an alkyl group, ma=0 and na=1.

A group wherein, in formula (1), R^(a1) and R^(a2) are eachindependently an alkyl group, R^(a3) is an adamantyl group, ma=0 andna=1.

Specific examples of the group (1) include the following groups. *represents a bonding site.

Specific examples of the group (2) include the following groups. *represents a bonding site.

The monomer (a1) is preferably a monomer having an acid-labile group andan ethylenic unsaturated bond, and more preferably a (meth acrylicmonomer having an acid-labile group.

Of the (meth) acrylic monomers having an acid-labile group, those havingan alicyclic hydrocarbon group having 5 to 20 carbon atoms arepreferably exemplified. When a resin including a structural unit derivedfrom a monomer (a1) having a bulky structure such as an alicyclichydrocarbon group is used in a resist composition, it is possible toimprove the resolution of a resist pattern.

The structural unit derived from a (meth)acrylic monomer having a group(1) is preferably a structural unit represented by formula (a1-0)(hereinafter sometimes referred to as structural unit (a1-0)), astructural unit represented by formula (a1-1) (hereinafter sometimesreferred to as structural unit (a1-1)) or a structural unit representedby formula (a1-2) (hereinafter sometimes referred to as structural unit(a1-2)). The structural unit is more preferably at least one structuralunit selected from the group consisting of a structural unit (a1-1) anda structural unit (a1-2). These structural units may be used alone, ortwo or more structural units may be used in combination:

wherein, in formula (a1-0), formula (a1-1) and formula (a1-2),

L^(a01), L^(a1) and L^(a2) each independently represent —O— or *—O—(CH₂)_(k1)—CO—O—, k1 represents an integer of 1 to 7, and * represents abonding site to —CO—,

R^(a01), R^(a4) and R^(a5) each independently represent a hydrogen atomor a methyl group,

R^(a02), R^(a03) and R^(a04) each independently represent an alkyl grouphaving 1 to 8 carbon atoms, an alicyclic hydrocarbon group having 3 to18 carbon atoms, or groups obtained by combining these groups,

R^(a6) and R^(a7) each independently represent an alkyl group having 1to 8 carbon atoms, an alicyclic hydrocarbon group having 3 to 18 carbonatoms, or groups formed by combining these groups,

-   -   m1 represents an integer of 0 to 14,    -   n1 represents an integer of 0 to 10, and    -   n1′ represents an integer of 0 to 3.

R^(a01), R^(a4) and R^(a6) are preferably a methyl group.

L^(a01), L^(a1) and L^(a2) are preferably an oxygen atom or*—O—(CH₂)_(k01)—CO—O— (k01 is preferably an integer of 1 to and morepreferably^(.) 1), and more preferably an oxygen atom.

Examples of the alkyl group., the alicyclic hydrocarbon group and groupsobtained by combining these groups in R^(a02), R^(a03), R^(a04), R^(a06)and R^(a07) include the same groups as mentioned for R_(a1), R^(a2) andR^(a3) of formula (1).

The alkyl group in R^(a02), R^(a03) and R^(a04) is preferably an alkylgroup having 1 to 6 carbon atoms, more preferably a methyl group or anethyl group, and still more preferably a methyl group.

The alkyl group in R^(a6) and R^(a7) is preferably an alkyl group having1 to 6 carbon atoms, more preferably a methyl group, an ethyl group oran isopropyl group, and still more preferably an ethyl group or anisopropyl group.

The number of carbon atoms of the alicyclic hydrocarbon group forR^(a02), R^(a03), R^(a04), R^(a6) and R^(a7) is preferably 5 to 12, andmore preferably 5 to 10.

The total number of carbon atoms of the group obtained by combining thealkyl group and the alicyclic hydrocarbon group is preferably 18 orless.

R^(a02) and R^(a03) are preferably an alkyl group having 1 to 6 carbonatoms, and more preferably a methyl group or an ethyl group.

R^(a04) is preferably an alkyl group having 1 to 6 carbon atoms or analicyclic hydrocarbon group having 5 to 12 carbon atoms, and morepreferably a methyl group, an ethyl group, a cyclohexyl group or anadamantyl group.

Preferably, R^(a6) and R^(a7) each independently represent an alkylgroup having 1 to 6 carbon atoms, more preferably a methyl group, anethyl group or an isopropyl group, and still more preferably an ethylgroup or an isopropyl group.

m1 is preferably an integer of 0 to 3, and more preferably 0 or 1.

n1 is preferably an integer of 0 to 3, and more preferably 0 or 1.

n1′ is preferably 0 or 1.

Examples of the structural unit (a1-0) include a structural unitrepresented by any one of formula (a1-0-1) to formula (a1-0-12) and astructural unit in which a methyl group corresponding to R^(a01) in thestructural unit (a1-0) is substituted with a hydrogen atom, and astructural unit represented by any one of formula (a1-0-1) to formula(a1-0-10) is preferable.

Examples of the structural unit (a1-1) include structural units derivedfrom the monomers mentioned in JP 2010-204646 A. Of these, a structuralunit represented by any one of formula (a1-1-1) to formula (a1-1-4) anda structural unit in which a methyl group corresponding to R^(a4) in thestructural unit (a1-1) is substituted with a hydrogen atom arepreferable, and a structural unit represented by any one of formula(a1-1-1) to formula (a1-1-4) is more preferable.

Examples of the structural unit (a1-2) include a structural unitrepresented by any one of formula (a1-2-1) to formula (a1-2-6) and astructural unit in which a methyl group corresponding to R^(a5) in thestructural unit (a1-2) is substituted with a hydrogen atom, and astructural unit represented by any one of formula (a1-2-2), formula(a1-2-5) and formula (a1-2-6) is preferable.

When the resin (A) includes the structural unit (a1-0), the content isusually 5 to 60 mol %, preferably 5 to 50 mol %, and more preferably 10to 40 mol %, based on all structural units of the resin (A).

When the resin (A) includes the structural unit (a1-1) and/or thestructural unit (a1-2), the total content thereof is usually 5 to 90 mol%, preferably 10 to 85 mol %, more preferably 15 to 80 mol %, still morepreferably 15 to 70 mol %, and yet more preferably 15 to 60 mol %, basedon all structural units of the resin (A).

Examples of the structural unit having a group (2) in the structuralunit (a1) include a structural unit represented by formula (a1-4)(hereinafter sometimes referred to as “structural unit (a1-4)”):

wherein, in formula (a1-4),

R^(a32) represents a hydrogen atom, a halogen atom, or an alkyl grouphaving 1 to 6 carbon atoms which may have a halogen atom,

R^(a33) represents a halogen atom, a hydroxy group, an alkyl grouphaving 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms,an alkylcarbonyl group having 2 to 4 carbon atoms, an alkylcarbonyloxygroup having 2 to 4 carbon atoms, an acryloyloxy group or amethacryloyloxy group,

1a represents an integer of 0 to 4, and when la is 2 or more, aplurality of R^(a33) may be the same or different form each other, and

R^(a34) and R^(a35) each independently represent a hydrogen atom or ahydrocarbon group having 1 to 12 carbon atoms, R^(a36) represents ahydrocarbon group having 1 to 20 carbon atoms, or R^(a35) and R^(a36)are bonded each other to form a divalent hydrocarbon group having 2 to20 carbon atoms together with —C—O— to which R^(a35) and R^(a36) arebonded, and —CH₂— included in the hydrocarbon group and the divalenthydrocarbon group may be replaced by —O— or —S—.

Examples of the alkyl group in R^(a32) and R^(a33) include a methylgroup, an ethyl group, a propyl group, an isopropyl group, a butylgroup, a pentyl group and a hexyl group. The alkyl group is preferablyan alkyl group having 1 to 4 carbon atoms, more preferably a methylgroup or an ethyl group, and still more preferably a methyl group.

Examples of the halogen atom in R^(a32) and R^(a33) include a fluorineatom, a chlorine atom and a bromine atom.

Examples of the alkyl group having 1 to 6 carbon atoms which may have ahalogen atom include a trifluoromethyl group, a difluoromethyl group, amethyl group, a perfluoroethyl group, a 2,2,2-trifluoroethyl group, a1,1,2,2-tetrafluoroethyl group, an ethyl group, a perfluoropropyl group,a 2,2,3,3,3-pentafluoropropyl group, a propyl group, a perfluorobutylgroup, a 1,1,2,2,3,3,4,4-octafluorobutyl group, a butyl group, aperfluoropentyl group, a 2,2,3,3,4,4,5,5,5-nonafluoropentyl group, apentyl group, a hexyl group, a perfluorohexyl group and the like.

Examples of the alkoxy group include a methoxy group, an ethoxy group, apropoxy group, a butoxy group, a pentyloxy group and a hexyloxy group.Of these, an alkoxy group having 1 to 4 carbon atoms is preferable, amethoxy group or an ethoxy group is more preferable, and a methoxy groupis still more preferable.

Examples of the alkylcarbonyl group include an acetyl group, a propionylgroup and a butyryl group.

Examples of the alkylcarbonyloxy group include an acetyloxy group, apropionyloxy group, a butyryloxy group and the like.

Examples of the hydrocarbon group in R^(a34), R^(a35) and R^(a36)include an alkyl group, an alicyclic hydrocarbon group, an aromatichydrocarbon group, and groups obtained by combining these groups.

Examples of the alkyl group include a methyl group, an ethyl group, apropyl group, a butyl group, a pentyl group, a hexyl group, a heptylgroup, an octyl group and the like.

The alicyclic hydrocarbon group may be either monocyclic or polycyclic.Examples of the monocyclic alicyclic hydrocarbon group includecycloalkyl groups such as a cyclopentyl group, a cyclohexyl group, acycloheptyl group and a cyclooctyl group. Examples of the polycyclicalicyclic hydrocarbon group include a decahydronaphthyl group, anadamantyl group, a norbornyl group, and the following groups (*represents a bonding site).

Examples of the aromatic hydrocarbon group include aryl groups such as aphenyl group, a naphthyl group, an anthryl group, a biphenyl group and aphenanthryl group.

Examples of the combined group include a group obtained by combining theabove-mentioned alkyl group and alicyclic hydrocarbon group (e.g., acycloalkylalkyl group), an aralkyl group such as a benzyl group, anaromatic hydrocarbon group having an alkyl group (a p-methylphenylgroup, a p-tert-butylphenyl group, a tolyl group, a xylyl group, acumenyl group, a mesityl group, a 2,6-diethylphenyl group, a2-methyl-6-ethylphenyl group, etc.), an aromatic hydrocarbon grouphaving an alicyclic hydrocarbon group (a p-cyclohexylphenyl group, ap-adamantylphenyl group, etc.), an aryl-cycloalkyl group such as aphenylcyclohexyl group, and the like. Particularly, examples of R^(a36)include an alkyl group having 1 to 18 carbon atoms, an alicyclichydrocarbon group having 3 to 18 carbon atoms, an aromatic hydrocarbongroup having 6 to 18 carbon atoms, or groups obtained by combining thesegroups.

In formula (a1-4), R^(a32) is preferably a hydrogen atom,

R^(a33) is preferably an alkoxy group having 1 to 4 carbon atoms, morepreferably a methoxy group and an ethoxy group, and still morepreferably a methoxy group,

1a is preferably 0 or 1, and more preferably 0,

R^(a34) is preferably a hydrogen atom, and

R^(a35) is preferably an alkyl group having 1 to 12 carbon atoms or analicyclic hydrocarbon group, and more preferably a methyl group or anethyl group.

The hydrocarbon group for R^(a36) is preferably an alkyl group having 1to 18 carbon atoms, an alicyclic hydrocarbon group having 3 to 18 carbonatoms, an aromatic hydrocarbon group having 6 to 18 carbon atoms, orgroups formed by combining these groups, more preferably an alkyl grouphaving 1 to 18 carbon atoms, an alicyclic hydrocarbon group having 3 to18 carbon atoms or an aralkyl group having 7 to 18 carbon atoms. Thealkyl group and the alicyclic hydrocarbon group in R^(a36) arepreferably unsubstituted. The aromatic hydrocarbon group in R^(a36) ispreferably an aromatic ring having an aryloxy group having 6 to 10carbon atoms.

—OC(R^(a34))(R^(a35))—O—R^(a36) in the structural unit (a1-4) iseliminated by contact with an acid (e.g., p-toluenesulfonic acid) toform a hydroxy group.

The structural unit (a1-4) includes, for example, structural unitsderived from the monomers mentioned in JP 2010-204646 A. The structuralunit preferably includes structural units represented by formula(a1-4-1) to formula (a1-4-12) and a structural unit in which a hydrogenatom corresponding to R^(a32) in the constitutional unit (a1-4) issubstituted with a methyl group, and more preferably structural unitsrepresented by formula (a1-4-1) to formula (a1-4-5) and formula(a1-4-10).

When the resin (A) includes the structural unit (a1-4), the content ispreferably 5 to 60 mol %, more preferably 5 to 50 mol %, and still morepreferably 10 to 40 mol %, based on the total of all structural units ofthe resin (A).

The structural unit (a1) also includes, for example, a structural unitrepresented by formula (a1-0X) (hereinafter sometimes referred to asstructural unit (a1-0X)):

wherein, in formula (a1-0X),

R^(x1) represents a hydrogen atom or a methyl group,

R^(x2) and R^(x2) each independently represent a saturated hydrocarbongroup having 1 to 6 carbon atoms, and

Ar^(x1) represents an aromatic hydrocarbon group having 6 to 36 carbonatoms.

Examples of the saturated hydrocarbon group for R^(x2) and R^(x2)include an alkyl group, an alicyclic hydrocarbon group, and groupsformed by combining these groups.

Examples of the alkyl group include a methyl group, an ethyl group, ann-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group,a tert-butyl group, a pentyl group, a hexyl group and the like.

The alicyclic hydrocarbon group may be either monocyclic or polycyclic,and examples of the monocyclic alicyclic hydrocarbon group include acyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexylgroup and the like.

Examples of the aromatic hydrocarbon group for Ar^(x2) include arylgroups having 6 to 36 carbon atoms such as a phenyl group, a naphthylgroup and an anthryl group.

The aromatic hydrocarbon group has preferably 6 to 24 carbon atoms, andmore preferably 6 to 18 carbon atoms, and is still more preferably aphenyl group.

Ar^(x1) is preferably an aromatic hydrocarbon group having 6 to 18carbon atoms, more preferably a phenyl group or a naphthyl group, andstill more preferably a phenyl group.

Preferably, R^(x1), R^(x2) and R^(x2) each independently represent amethyl group or an ethyl group, and more preferably a methyl group.

Examples of the structural unit (a1-0X) include the following structuralunits and a structural unit in which a methyl group corresponding toR^(x1) in the structural unit (a1-0X) is substituted with a hydrogenatom. The structural unit (a1-0X) preferably includes a structural unit(a1-0X-1) to a structural unit (a1-0X-3).

When the resin (A) includes the structural unit (a1-0X), the content ispreferably 5 to 60 mol %, more preferably 5 to 50 mol %, and still morepreferably 10 to 40 mol %, based on all monomers in the resin (A).

The resin. (A) may include two or more structural units (a1-0X).

Examples of the structural unit (a1) also include the followingstructural units.

When the resin includes the above-mentioned structural unit, the contentis preferably 5 to 60 mol %, more preferably 5 to 50 mol %, and stillmore preferably 10 to 40 moll, based on all structural units of theresin (A).

<Structural Unit(s)>

The structural unit(s) is derived from a monomer having no acid-labilegroup (hereinafter sometimes referred to as “monomer(s)”). It ispossible to use, as the monomer from which the structural unit(s) isderived, a monomer having no acid-labile group known in the resistfield.

The structural unit(s) preferably has a hydroxy group or a lactone ring.When a resin including a structural unit having a hydroxy group andhaving no acid-labile group (hereinafter sometimes referred to as“structural unit (a2)”) and/or a structural unit having a lactone ringand having no acid-labile group (hereinafter sometimes referred to as“structural unit (a3)”) is used in the resist composition of the presentinvention, it is possible to improve the resolution of a resist patternand the adhesion to a substrate.

<Structural Unit (a2)>

The hydroxy group possessed by the structural unit (a2) may be either analcoholic hydroxy group or a phenolic hydroxy group.

When a resist pattern is produced from the resist composition of thepresent invention, in the case of using, as an exposure source, highenergy rays such as KrF excimer laser (248 nm), electron beam or extremeultraviolet (EUV) light, it is preferable to use a structural unit (a2)having a phenolic hydroxy group as the structural unit (a2). When usingArF excimer laser (193 nm) or the like, a structural unit (a2) having analcoholic hydroxy group is preferably used as the structural unit (a2),and it is more preferably use a structural unit (a2-1) mentioned later.The structural unit (a2) may be included alone, or two or morestructural units may be included.

In the structural unit (a2), examples of the structural unit having aphenolic hydroxy group include a structural unit represented by formula(a2-A) (hereinafter sometimes referred to as “structural unit (a2-A)”):

wherein, in formula (a2-A).

R^(a50) represents a hydrogen atom, a halogen atom or an alkyl grouphaving 1 to 6 carbon atoms which may have a halogen atom,

R^(a51) represents a halogen atom, a hydroxy group, as alkyl grouphaving 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms,an alkylcarbonyl group having 2 to 4 carbon atoms, an alkylcarbonyloxygroup having 2 to 4 carbon atoms or an acryloyloxy group or amethacryloyloxy group,

A^(a50) represents a single bond or *—X^(a51)-(A^(a52)-X^(a52))_(nb)-,and * represents a bond to carbon atoms to which —R^(a50) is bonded,

A^(a52) represents an alkanediyl group having 1 to 6 carbon atoms,

X^(a31) and X^(a32) each independently represent —O—, —CO—O— or —O—CO—,

nb represents 0 or 1, and

mb represents an integer of 0 to 4, and when mb is an integer of 2 ormore, a plurality of R^(a51) may be the same or different from eachother.

Examples of the halogen atom in R^(a50) include a fluorine atom, achlorine atom and a bromine atom.

Examples of the alkyl group having 1 to 6 carbon atoms which may have ahalogen atom in R^(a50) include a trifluoromethyl group, adifluoromethyl group, a methyl group, a perfluoroethyl group, a2,2,2-trifluoroethyl group, a 1,1,2,2-tetrafluoroethyl group, an ethylgroup, a perfluoropropyl group, a 2,2,3,3,3-pentafluoropropyl group, apropyl group, a perfluorobutyl group, a 1,1,2,2,3,3,4,4-octafluorobutylgroup, a butyl group, a perfluoropentyl group, a2,2,3,3,4,4,5,5,5-nonafluoropentyl group, a pentyl group, a hexyl groupand a perfluorohexyl group.

R^(a50) is preferably a hydrogen atom or an alkyl group having 1 to 4carbon atoms, more preferably a hydrogen atom, a methyl group or anethyl group, and still more preferably a hydrogen atom or a methylgroup.

Examples of the alkyl group in R^(a51) include a methyl group, an ethylgroup, a propyl group, an isopropyl group, a butyl group, a sec-butylgroup, a tert-butyl group, a pentyl group and a hexyl group.

Examples of the alkoxy group in R^(a51) include a methoxy group, anethoxy group, a propoxy group, an isopropoxy group, a butoxy group, asec-butoxy group and a tert-butoxy group. An alkoxy group having 1 to 4carbon atoms is preferable, a methoxy group or an ethoxy group is morepreferable, and a methoxy group is still more preferable.

Examples of the alkylcarbonyl group in R^(a51) include an acetyl group,a propionyl group and a butyryl group.

Examples of the alkylcarbonyloxy group in R^(a51) include an acetyloxygroup, a propionyloxy group and a butyryloxy group.

R^(a51) is preferably a methyl group.

Examples of * -X^(a51)-(A^(a52)-X^(a52))_(nb)- include *—O—, *—CO—O—,*—O—CO—, *—CO—O-A^(a52)-CO—O—, *—O—CO-A⁵²-O—, *—O-A^(a52)-CO—O—,*—CO—O-A^(a52)-O—CO— and *—O—CO-A^(a52)-O—CO—. Of these, *—CO—O—,*—CO—O-A^(a52)-CO—O— or *—O-A^(a52)-CO—O— preferable.

Examples of the alkanediyl group include a methylene group, an ethylenegroup, a propane-1,3-diyl group, a propane-1,2-diyl group, abutane-1,4-diyl group, a pentane-1,5-diyl group, a hexane-1,6-diylgroup, a butane-1,3-diyl group, a 2-methylpropane-1,3-diyl group, a2-methylpropane-1,2-diyl group, a pentane-1,4-diyl group and a2-methylbutane-1,4-diyl group.

A^(a52) is preferably a methylene group or an ethylene group.

A^(a50) is preferably a single bond, *—CO—O— or *—CO—O-A^(a52)-CO—O—,more preferably a single bond, *—CO—O— or *—CO—O—CH₂—CO—O—, and stillmore preferably a single bond or *—CO—O—.

mb is preferably a 0, 1 or 2, more preferably 0 or 1, and particularlypreferably 0.

The hydroxy group is preferably bonded to the ortho-position or thepara-position of a benzene ring, and more preferably the para-position.

Examples of the structural unit (a2-A) include structural units derivedfrom the monomers mentioned in JP 2010-204634 A and JP 2012-12577 A.

Examples of the structural unit (a2 -A) include structural unitsrepresented by formula (a2-2-1) to formula (a2-2-6) and a structuralunit in which a methyl group corresponding to R^(a50) in the structuralunit (a2-A) is substituted with a hydrogen atom in structural unitsrepresented by formula (a2-2-1) to formula (a2-2-6). The structural unit(a2-A) is preferably a structural unit represented by formula (a2-2-1),a structural unit represented by formula (a2-2-3), a structural unitrepresented by formula (a2-2-6), and a structural unit in which a methylgroup corresponding to R^(a50) in the structural unit (a2-A) issubstituted with a hydrogen atom in the structural unit represented byformula (a2-2-1), the structural unit represented by formula (a2-2-3) orthe structural unit represented by formula (a2-2-6).

When the structural unit (a2-A) is included in the resin (A), thecontent of the structural unit (a2-A) is preferably 5 to 80 mol %, morepreferably 10 to 70 mol %, still more preferably 15 to 65 mol %, and yetmore preferably 20 to 65 mol %, based on all structural units.

The structural unit (a2-A) can be included in the resin (A) bypolymerizing, for example, with a structural unit (a1-4) and treatingwith an acid such as p-toluenesulfonic acid. The structural unit (a2-A)can also be included in the resin by polymerizing with acetoxystyreneand treating with an alkali such as tetramethylammonium hydroxide.

Examples of the structural unit having an alcoholic hydroxy group in thestructural unit (a2) include a structural unit represented by formula(a2-1) (hereinafter sometimes referred to as “structural unit (a2-1)”).

In formula (a2-1).

L^(a3) represents —O— or *—O—(CH₂)_(k2)—CO—O—,

k2 represents an integer of 1 to 7, and represents a bonding site to—CO—.

R^(a14) represents a hydrogen atom or a methyl group.

R^(a13) and R^(a16) each independently represent a hydrogen atom, amethyl group or a hydroxy group.

o1 represents an integer of 0 to 10.

In formula (a2-1), L^(a3) is preferably —O— or —O—(CH₂)_(f1)—CO—O— (f1represents an integer of 1 to 4), and more preferably —O—,

R^(a14) is preferably a methyl group,

R^(a15) is preferably a hydrogen atom,

R^(a16) is preferably a hydrogen atom or a hydroxy group, and

o1 is preferably an integer of 0 to 3, and more preferably 0 or 1.

The structural unit (a2-1) includes, for example, structural unitsderived from the monomers mentioned in JP 2010-204646 A. A structuralunit represented by any one of formula (a2-1-1) to formula (a2-1-6) ispreferable, a structural unit represented by any one of formula (a2-1-1)to formula (a2-1-4) is more preferable, and a structural unitrepresented by formula (a2-1-1) or formula (a2-1-3) is still morepreferable.

When the resin (A) includes the structural unit (a2-1), the content isusually 1 to 45 mol %, preferably 1 to 40 mol %, more preferably 1 to 35mol %, still more preferably 1 to 20 mol %, and yet more preferably 1 to10 mol %, based on all structural units of the resin (A).

<Structural Unit (a3)>

The lactone zing possessed by the structural unit (a3) may be amonocyclic ring such as a β-propiolactone ring, a γ-butyrolactone ringor a δ-valerolactone ring, or a condensed. ring of a monocyclic lactonering and the other ring. Preferably, a γ-butyrolactone ring, anadamantanelactone ring or a bridged ring including a γ-butyrolactonering structure (e.g., a structural unit represented by the followingformula (a3-2)) is exemplified.

The structural unit (a3) is preferably a structural unit represented byformula (a3-1), formula (a3-2), formula (a3-3) or formula (a3-4). Thesestructural units may be included alone, or two or more structural unitsmay be included:

wherein, in formula (a3-1), formula (a3-2), formula (a3-3) and formula(a3-4),

L^(a4), L^(a5) and L^(a6) each independently represent —O— or a grouprepresented by *—O—(CH₂)_(k3)—CO—O— (k3 represents an integer of 1 to 7)

L^(a7) represents —O—, —O-L^(a8)-O—, *—O-L^(a8)-CO—O—,*—O-L^(a8)-CO—O-L^(a9)-CO—O— or *—O-L^(a8)-O—CO-L^(a9)-O—,

L^(a8) and L^(a9) each independently represent an alkanediyl grouphaving 1 to 6 carbon atoms,

* represents a bonding site to a carbonyl group,

R^(a18), R^(a19) and R^(a20) each independently represent a hydrogenatom or a methyl group,

R^(a24) represents an alkyl group having 1 to 6 carbon atoms which mayhave a halogen atom, a hydrogen atom or a halogen atom,

X^(a3) represents —CH₂— or an oxygen atom,

R^(a21) represents an aliphatic hydrocarbon group having 1 to 4 carbonatoms,

R^(a22), R^(a23) and R^(a25) each independently represent a carboxygroup, a cyano group or an aliphatic hydrocarbon group having 1 to 4carbon atoms,

p1 represents an integer of 0 to 5,

q1 represents an integer of 0 to 3,

r1 represents an integer of 0 to 3,

w1 represents an integer of 0 to 8, and

when p1, q1, r1 and/or w1 is/are 2 or more, a plurality of R^(a21),R^(a22), R^(a23) and/or R^(a25) may be the same or different from eachother.

Examples of the aliphatic hydrocarbon group in Ra²¹, R^(a22), R^(a23)and R^(a25) include alkyl groups such as a methyl group, an ethyl group,a propyl group, an isopropyl group, a butyl group, a sec-butyl group anda tert-butyl group.

Examples of the halogen atom in R^(a24) include a fluorine atom, achlorine atom, a bromine atom and an iodine atom.

Examples of the alkyl group in R^(a24) include a methyl group, an ethylgroup, a propyl group, an isopropyl group, a butyl group, a sec-butylgroup, a tert-butyl group, a pentyl group and a hexyl group, and thealkyl group is preferably an alkyl group having 1 to 4 carbon atoms, andmore preferably a methyl group or an ethyl group.

Examples of the alkyl group having a halogen atom in R^(a24) include atrifluoromethyl group, a perfluoroethyl group, a perfluoropropyl group,a perfluoroisopropyl group, a perfluorobutyl group, a perfluorosec-butylgroup, a perfluorotert-butyl group, a perfluoropentyl group, aperfluorohexyl group, a trichloromethyl group, a tribromomethyl group, atriiodomethyl group and the like.

Examples of the alkanediyl group in L^(a8) and L^(a9) include amethylene group, an ethylene group, a propane-1,3-diyl group, apropane-1,2-diyl group, a butane-1,4-diyl group, a pentane-1,5-diylgroup, a hexane-1,6-diyl group, a butane-1,3-diyl group, a2-methylpropane-1,3-diyl group, a 2-methylpropane-1,2-diyl group, apentane-1,4-diyl group and a 2-methylbutane-1,4-diyl group and the like.

In formula (a3-1) to formula (a3-3), preferably, L^(a4) to L^(a6) areeach independently —O— or a group in which k3 is an integer of 1 to 4 in*—O—(CH₂)_(k3)—CO—O—, more preferably —O— and *—O—CH₂—CO—O—, and stillmore preferably an oxygen atom,

R^(a18) to R^(a21) are preferably a methyl group,

preferably, R^(a22) and R^(a23) are each independently a carboxy group,a cyano group or a methyl group, and

preferably, p1, q1 and r1 are each independently an integer of 0 to 2,and more preferably 0 or 1.

In formula (a3-4), R^(a24) is preferably a hydrogen atom or an alkylgroup having 1 to 4 carbon atoms, more preferably a hydrogen atom, amethyl group or an ethyl group, and still more preferably a hydrogenatom or a methyl group,

R^(a25) is preferably a carboxy group, a cyano group or a methyl group,

L^(a7) is preferably —O— or *—O-L^(a8)-CO—O—, and more preferably —O—,—O—CH₂—CO—O— or —O—C₂H₄—CO—O—, and

w1 is preferably an integer of 0 to 2, and more preferably 0 or 1.

Particularly, formula (a3-4) is preferably formula (a3-4)′:

wherein R^(a24) and L^(a7) are the same as defined above.

Examples of the structural unit (a3) include structural units derivedfrom the monomers mentioned in JP 2010-204646 A, the monomers mentionedin JP 2000-122294 A and the monomers mentioned in JP 2012-41274 A. Thestructural unit (a3) is preferably a structural unit represented by anyone of formula (a3-1-1), formula (a3-1-2), formula (a3-2-1), formula(a3-2-2), formula (a3-3-1), formula (a3-3-2) and formula (a3-4-1) toformula (a3-4-12), and structural units in which methyl groupscorresponding to R^(a18), R^(a19), R^(a20) and R^(a24) in formula (a3-1)to formula (a3-4) are substituted with hydrogen atoms in the abovestructural units.

When the resin (A) includes the structural unit (a3), the total contentis usually 2 to 70 mol %, preferably 3 to 60 mol %, and still morepreferably 5 to 50 mol %, based on all structural units of the resin(A).

Each content of the structural unit (a3-1), the structural unit (a3-2),the structural unit (a3-3) or the structural unit (a3-4) is preferably 1to 60 mol %, more preferably 1 to 50 mol %, and still more preferably 1to 40 mol %, based on all structural units of the resin (A).

<Structural Unit (a4)>

Examples of the structural unit (a4) include the following structuralunit:

wherein, in formula (a4),

R⁴¹ represents a hydrogen atom or a methyl group, and

R⁴² represents a saturated hydrocarbon group having 1 to 24 carbon atomshaving a fluorine atom, and —CH₂— included in the saturated hydrocarbongroup may be replaced by —O— or —CO.

Examples of the saturated hydrocarbon group represented by R⁴² include achain saturated hydrocarbon group and a monocyclic or polycyclicalicyclic saturated hydrocarbon group, and groups formed by combiningthese groups.

Examples of the chain hydrocarbon group include a methyl group, an ethylgroup, a propyl group, a butyl group, a pentyl group, a hexyl group, aheptyl group, as octyl group, a decyl group, a dodecyl group, apentadecyl group, a hexadecyl group, a heptadecyl group and an octadecylgroup.

Examples of the monocyclic or polycyclic alicyclic hydrocarbon groupinclude cycloalkyl groups such as a cyclopentyl group, a cyclohexylgroup, a cycloheptyl group and a cyclooctyl group; and polycyclicalicyclic hydrocarbon groups such as a decahydronaphthyl group, anadamantyl group, a norbornyl group and the following groups (*represents a bonding site).

Examples of the group formed by combination include groups formed bycombining one or more alkyl groups or one or more alkanediyl groups withone or more alicyclic saturated hydrocarbon groups, and include analkanediyl group-alicyclic hydrocarbon group, an alicyclic hydrocarbongroup-alkyl group, an alkanediyl group-alicyclic hydrocarbon group-alkylgroup and the like.

Examples of the structural unit (a4) include a structural unitrepresented by at least one selected from the group consisting offormula (a4-0), formula (a4-1), formula (a4-2), formula (a4-3) andformula (a4-4):

wherein, in formula (a4-0),

R⁵ represents a hydrogen atom or a methyl group,

L^(4a) represents a single bond or a divalent aliphatic hydrocarbongroup having 1 to 4 carbon atoms,

L^(3a) represents a perfluoroalkanediyl group having 1 to 8 carbon atomsor a perfluorocycloalkanediyl group having 3 to 12 carbon atoms, and

R⁶ represents a hydrogen atom or a fluorine atom.

Examples of the divalent aliphatic hydrocarbon group in L^(4a) includelinear alkanediyl groups such as a methylene group, an ethylene group, apropane-1,3-diyl group and a butane-1,4-diyl group; and branchedalkanediyl groups such as an ethane-1,1-diyl group, a propane-1, 2-diylgroup, a butane-1,3-diyl group, a 2-methylpropane-1,3-diyl group and a2-methylpropane-1,2-diyl group.

Examples of the perfluoroalkanediyl group in L^(3a) include adifluoromethylene group, a perfluoroethylene group, aperfluoropropane-1,1-diyl group, a perfluoropropane-1,3-diyl group, aperfluoropropane-1,2-diyl group, a perfluoropropane-2,2-diyl group, aperfluorobutane-1,4-diyl group, a perfluorobutane-2,2-diyl group, aperfluorobutane-1,2-diyl group, a perfluoropentane-1,5-diyl group, aperfluoropentane-2,2-diyl group, a perfluoropentane-3,3-diyl group, aperfluorohexane-1,6-diyl group, a perfluorohexane-2,2-diyl group, aperfluorohexane-3,3-diyl group, a perfluoroheptane-1,7-diyl group, aperfluoroheptane-2,2-diyl group, a perfluoroheptane-3,4-diyl group, aperfluoroheptane-4,4-diyl group, a perfluorooctane-1,8-diyl group, aperfluorooctane-2,2-diyl group, a perfluorooctane-3,3-diyl group, aperfluorooctane-4,4-diyl group and the like.

Examples of the perfluorocycloalkanediyl group in L^(3a) include aperfluorocyclohexanediyl group, a perfluorocyclopentanediyl group, aperfluorocycloheptanediyl group, a perfluoroadamantanediyl group and thelike.

L^(3a) is preferably a single bond, a methylene group or an ethylenegroup, and more preferably a single bond or a methylene group.

L^(3a) is preferably a perfluoroalkanediyl group having 1 to 6 carbonatoms, and more preferably a perfluoroalkanediyl group having 1 to 3carbon atoms.

Examples of the structural unit (a4-0) include the following structuralunits, and structural units in which a methyl group corresponding toR^(5a) in the structural unit (a4-0) in the following structural unitsis substituted with a hydrogen atom:

wherein, in formula (a4-1),

R^(a41) represents a hydrogen atom or a methyl group,

R^(a42) represents a saturated hydrocarbon group having 1 to 20 carbonatoms which may have a substituent, and —CH₂— included in the saturatedhydrocarbon group may be replaced by —O— or —CO—,

A^(a41) represents an alkanediyl group having 1 to 6 carbon atoms whichmay have a substituent or a group represented by formula (a-g1) in whichat least one of A^(a41) and R^(a42) has, as a substituent, a halogenatom (preferably a fluorine atom):

[wherein, in formula (a-g1),

a represents 0 or 1,

A^(a42) and A^(a44) each independently represent a divalent saturatedhydrocarbon group having 1 to 5 carbon atoms which may have asubstituent,

A^(a43) represents a single bond or a divalent aliphatic hydrocarbongroup having 1 to 5 carbon atoms which may have a substituent,

X^(a41) and X^(a42) each independently represent —O—, —CO—, —CO—O— or—O—CO—, in which the total number of carbon atoms of A^(a42), A^(a43),A^(a44), X^(a41) and X^(a42) is 7 or less], and

* is a bonding site and at the right side is a bonding site to—O—CO—R^(a42).

Examples of the saturated hydrocarbon group in R^(a42) include a chainsaturated hydrocarbon group and a monocylic or a polycyclic alicyclicsaturated hydrocarbon group, and groups formed by combining thesegroups.

Examples of the chain saturated hydrocarbon group include a methylgroup, an ethyl group, a propyl group, a butyl group, a pentyl group, ahexyl group, a heptyl group, an octyl group, a decyl group, a dodecylgroup, a pentadecyl group, a hexadecyl group, a heptadecyl group and anoctadecyl group.

Examples of the monocyclic or polycyclic alicyclic saturated hydrocarbongroup include cycloalkyl groups such as a cyclopentyl group, acyclohexyl group, a cycloheptyl group and a cyclooctyl group; andpolycyclic alicyclic saturated hydrocarbon groups such as adecahydronaphthyl group, an adamantyl group, a norbornyl group and thefollowing groups (* represents a bonding site).

Examples of the group formed by combination include groups formed bycombining one or more alkyl groups or one or more alkanediyl groups withone or more alicyclic saturated hydrocarbon groups, and include analkanediyl group-alicyclic saturated hydrocarbon group, an alicyclicsaturated hydrocarbon group-alkyl group, an alkanediyl group-alicyclicsaturated hydrocarbon group-alkyl group and the like.

Examples of the substituent which may be possessed by R^(a42) include atleast one selected from a halogen atom and a group represented byformula (a-g3). Examples of the halogen atom include a fluorine atom, achlorine atom, a bromine atom and an iodine atom, and a fluorine atom ispreferable:

*—X^(a43)-A^(a45)   (a-g3)

wherein, in formula (a-g3),

X^(a43) represents an oxygen atom, a carbonyl group, *—C—CO— or *—CO—O—,

A^(a45) represents an aliphatic hydrocarbon group having 1 to 17 carbonatoms which may have a halogen atom, and

* represents a bonding site to R^(a42).

In R^(a42)-X^(a43)-A^(a45), when R^(a42) has no halogen atom, A^(a45)represents an aliphatic hydrocarbon group having 1 to 17 carbon atomswhich has at least one halogen atom.

Examples of the aliphatic hydrocarbon group A^(a45) include alkyl groupssuch as a methyl group, an ethyl group, a propyl group, a butyl group, apentyl group, a hexyl group, a heptyl group, a octyl group, a decylgroup, a dodecyl group, a pentadecyl group, a hexadecyl group, aheptadecyl group and an octadecyl group; monocyclic alicyclichydrocarbon groups such as a cyclopentyl group, a cyclohexyl group, acycloheptyl group and a cyclooctyl group; and polycyclic alicyclichydrocarbon groups such as a decahydronaphthyl group, an adamantylgroup, a norbornyl group and the following groups (* represents abonding site).

Examples of the group formed by combination include groups formed bycombining one or more alkyl groups or one or more alkanediyl groups withone or more alicyclic hydrocarbon groups, and include an alkanediylgroup-alicyclic hydrocarbon. group, an alicyclic hydrocarbon group-alkylgroup, an alkanediyl group-alicyclic hydrocarbon group-alkyl group andthe like.

R^(a42) is preferably an aliphatic hydrocarbon group which may have ahalogen atom, and more preferably an alkyl group having a halogen atomand/or an aliphatic hydrocarbon group having a group represented byformula (a-g3).

When R^(a42) is an aliphatic hydrocarbon group having a halogen atom, analiphatic hydrocarbon group having a fluorine atom is preferable, aperfluoroalkyl group or a perfluorocycloalkyl group is more preferable,a perfluoroalkyl group having 1 to 6 carbon atoms is still morepreferable, and a perfluoroalkyl group having 1 to 3 carbon atoms isparticularly preferable. Examples of the perfluoroalkyl group include aperfluoromethyl group, a perfluoroethyl group, a perfluoropropyl group,a perfluorobutyl group, a perfluoropentyl group, a perfluorohexyl group,a perfluoroheptyl group and a perfluorooctyl group. Examples of theperfluorocycloalkyl group include a perfluorocyclohexyl group and thelike.

When R^(a42) is an aliphatic hydrocarbon group having a grouprepresented by formula (a-g3), the total number of carbon atoms ofR^(a42) is preferably 15 or less, and more preferably 12 or less,including the number of carbon atoms included in the group representedby formula (a-g3). When having the group represented by formula (a-g3)as the substituent, the number thereof is preferably 1.

When R^(a42) is an aliphatic hydrocarbon group having the grouprepresented by formula (a-g3), R^(a42) is still more preferably a grouprepresented by formula (a-g2):

*-A^(a46)-X^(a44)-A^(a47)   (a-g2)

wherein, in formula (a-g2),

A^(a46) represents a divalent aliphatic hydrocarbon group having 1 to 17carbon atoms which may have a halogen atom,

X^(a44) represents **—O—CO— or **—CO—O— (** represents a bonding site toA^(a46)),

A^(a47) represents an aliphatic hydrocarbon group having 1 to 17 carbonatoms which may have a halogen atom,

the total number of carbon atoms of A^(a46), A^(a47) and X^(a44) is 18or less, and at least one of A^(a46) and A^(a47) has at least onehalogen atom, and

* represents a bonding site to a carbonyl group.

The number of carbon atoms of the aliphatic hydrocarbon group forA^(a46) is preferably 1 to 6, and more preferably 1 to 3.

The number of carbon atoms of the aliphatic hydrocarbon group forA^(a47) is preferably 4 to 15, and more preferably 5 to 12, and A^(a47)is still more preferably a cyclohexyl group or an adamantyl group.

Preferable structure of the group represented by formula (a-g2) is thefollowing structure (* is a bonding site to a carbonyl group).

Examples of the alkanediyl group in A^(a41) include linear alkanediylgroups such as a methylene group, an ethylene group, a propane-1,3-diylgroup, a butane-1,4-diyl group, a pentane-1,5-diyl group and ahexane-1,6-diyl group; and branched alkanediyl groups such as apropane-1,2-diyl group, a butane-1,3-diyl group, a2-methylpropane-1,2-diyl group, a 1-methylbutane-1,4-diyl group and a2-methylbutane-1,4-diyl group.

Examples of the substituent in the alkanediyl group for A^(a41) includea hydroxy group and an alkoxy group having 1 to 6 carbon atoms.

A^(a41) is preferably an alkanediyl group having1 to 4 carbon atoms,more preferably an alkanediyl group having 2 to 4 carbon atoms, andstill more preferably an ethylene group.

Examples of the divalent saturated hydrocarbon group represented byA^(a42), A^(a43) and A^(a44) in the group represented by formula (a-g1)include a linear or branched alkanediyl group and a monocyclic divalentalicyclic hydrocarbon group, and groups formed by combining analkanediyl group and a divalent alicyclic hydrocarbon group. Specificexamples thereof include a methylene group, an ethylene group, apropane-1,3-diyl group, a propane-1,2-diyl group, a butane-1,4-diylgroup, a 1-methylpropane-1,3-diyl group, a 2-methylpropane-1,3-diylgroup, a 2-methylpropane-1,2-diyl group and the like.

Examples of the substituent of the divalent saturated hydrocarbon grouprepresented by A^(a42), A^(a43) and A^(a44) include a hydroxy group andan alkoxy group having 1 to 6 carbon atoms.

s is preferably 0.

In a group represented by formula (a-g1), examples of the group in whichX^(a42) is —O—, —CO—, —CO—O— or —O—CO— include the following groups. Inthe following exemplification, * and ** each represent a bonding site,and ** is a bonding site to —O—CO—R^(a42).

Examples of the structural unit represented by formula (a4-1) includethe following structural units, and structural units in which a methylgroup corresponding to R^(a41) in the structural unit represented byformula (a4-1) in the following structural units is substituted with ahydrogen atom.

The structural unit represented by formula (a4-1) is preferably astructural unit represented by formula (a4-2):

wherein, in formula (a4-2),

R^(f5) represents a hydrogen atom or a methyl group,

L⁴⁴ represents an alkanediyl group having 1 to 6 carbon atoms, and —CH₂—included in the alkanediyl group may be replaced by —O— or —CO—,

R^(f6) represents a saturated hydrocarbon group having 1 to 20 carbonatoms having a fluorine atom, and

the upper limit of the total number of carbon atoms of L⁴⁴ and R⁶⁶ is21.

Examples of the alkanediyl group having 1 to 6 carbon atoms for L⁴⁴include the same groups as mentioned for the alkanediyl group inA^(a41).

Examples of the saturated hydrocarbon group for R^(f6) include the samegroups as mentioned for R^(a42).

The alkanediyl group having 1 to 6 carbon atoms in L⁴⁴ is preferably analkanediyl group having 2 to 4 carbon atoms, and more preferably anethylene group.

The structural unit represented by formula (a4-2) includes, for example,structural units represented by formula (a4-1-1) to formula (a4-1-11). Astructural unit in which a methyl group corresponding to R^(f5) in thestructural unit (a4-2) is substituted with a hydrogen atom is alsoexemplified as the structural unit represented by formula (a4-2).

Examples of the structural unit (a4) include a structural unitrepresented by formula (a4-3):

wherein, in formula (a4-3),

R^(f7) represents a hydrogen atom or a methyl group,

L⁵ represents an alkanediyl group having 1 to 6 carbon atoms,

A^(f13) represents a divalent saturated hydrocarbon group having 1 to 18carbon atoms which may have a fluorine atom,

X^(f12) represents *—O—CO— or *—CO—O— (* represents a bonding site toA^(f13)),

A^(f14) represents a saturated hydrocarbon group having 1 to 17 carbonatoms which may have a fluorine atom, and

at least one of A^(f13) and A^(f14) has a fluorine atom, and the upperlimit of the total number of carbon atoms of L⁵, A^(f13) and A^(f14) is20.

Examples of the alkanediyl group in L⁵ include those which are the sameas mentioned in the alkanediyl group for A^(a41).

The divalent saturated hydrocarbon group which may have a fluorine atomin A^(f13) is preferably a divalent aliphatic saturated hydrocarbongroup which may have a fluorine atom and a divalent aliphatic saturatedhydrocarbon group which may have a fluorine atom, and more preferably aperfluoroalkanediyl group.

Examples of the divalent aliphatic saturated hydrocarbon group which mayhave a fluorine atom include alkanediyl groups such as a methylenegroup, an ethylene group, a propanediyl group, a butanediyl group and apentanediyl group; and perfluoroalkanediyl groups such as adifluoromethylene group, a perfluoroethylene group, aperfluoropropanediyl group, a perfluorobutanediyl group and aperfluoropentanediyl group.

The divalent alicyclic hydrocarbon group which may have a fluorine atommay be either monocyclic or polycyclic. Examples of the monocyclic groupinclude a cyclohexanediyl group and a perfluorocyclohexanediyl group.Examples of the polycyclic group include an adamantanediyl group, anorbornanediyl group, a perfluoroadamantanediyl group and the like.

Examples of the saturated hydrocarbon group and the saturatedhydrocarbon group which may have a fluorine atom for A^(f14) include thesame groups as mentioned for R^(a42). Of these groups, preferred arefluorinated alkyl groups such as a trifluoromethyl group, adifluoromethyl group, a methyl group, a perfluoroethyl group, a2,2,2-trifluoroethyl group, a 1,1,2,2-tetrafluoroethyl group, an ethylgroup, a perfluoropropyl group, a 2,2,3,3,3-pentafluoropropyl group, apropyl group, a perfluorobutyl group, a 1,1,2,2,3,3,4,4-octafluorobutylgroup, a butyl group, a perfluoropentyl group, a2,2,3,3,4,4,5,5,5-nonafluoropentyl group, a pentyl group, a hexyl group,a perfluorohexyl group, a heptyl group, a perfluoroheptyl group, anoctyl group and a perfluorooctyl group; a cyclopropylmethyl group, acyclopropyl group, a cyclobutylmethyl group, a cyclopentyl group, acyclohexyl group, a perfluorocyclohexyl group, an adamantyl group, anadamantylmethyl group, an adamantyldimethyl group, a norbornyl group, anorbornyl methyl group, a perfluoroadamantyl group, aperfluoroadamantylmethyl group and the like.

In formula (a4-3), L⁵ is preferably an ethylene group.

The saturated hydrocarbon group for A^(f13) is preferably a groupincluding a chain hydrocarbon group having 1 to 6 carbon atoms and adivalent alicyclic hydrocarbon group having 3 to 12 carbon atoms, andmore preferably a chain hydrocarbon group having 2 to 3 carbon atoms.

The saturated hydrocarbon group for A^(f14) is preferably a groupincluding a chain hydrocarbon group having 3 to 12 carbon atoms and analicyclic hydrocarbon group having 3 to 12 carbon atoms, and morepreferably a group including a chain hydrocarbon group having 3 to 10carbon atoms and an alicyclic hydrocarbon group having 3 to 10 carbonatoms. Of these groups, A^(f14)is preferably a group including analicyclic hydrocarbon group having 3 to 12 carbon atoms, and morepreferably a cyclopropylmethyl group, a cyclopentyl group, a cyclohexylgroup, a norbornyl group and an adamantyl group.

The structural unit represented by formula (a4-3) includes, for example,structural units represented by formula (a4-1′-1) to formula.(a4-1′-11). A structural unit in which a methyl group corresponding toR^(f7) in the structural unit (a4-3) is substituted with a hydrogen atomis also exemplified as the structural unit represented by formula(a4-3).

The structural unit (a4) also includes a structural unit represented byformula (a4-4):

In formula (a4-4),

R^(f21) represents a hydrogen atom or a methyl group,

A^(f21) represents —(CH₂)_(j1)—, —(CH₂)_(j2)—O—(CH₂)_(j3)— or—(CH₂)_(j4)—CO—O—(CH₂)_(j5)—,

j1 to j5 each independently represent an integer of 1 to 6, and

R^(f22) represents a saturated hydrocarbon group having 1 to 10 carbonatoms which has a fluorine atom.

Examples of the saturated hydrocarbon group for R^(f22) include thosewhich are the same as the saturated hydrocarbon. group represented byR^(a42).

R^(f22) is preferably an alkyl group having 1 to 10 carbon atoms whichhas a fluorine atom or an alicyclic saturated hydrocarbon group having 1to 10 carbon atoms which. has a fluorine atom, more preferably an alkylgroup having 1 to 10 carbon atoms which has a fluorine atom, and stillmore preferably an alkyl group having 1 to 6 carbon atoms which has afluorine atom.

In formula (a4-4), A^(f21) is preferably —(CH₂)_(j1)—, more preferablyan ethylene group or a methylene group., and still more preferably amethylene group.

The structural unit represented by formula (a4-4) includes, for example,the following structural units and structural units in which a methylgroup corresponding to R^(f21) in the structural unit (a4-4) issubstituted with a hydrogen atom in structural units represented by thefollowing formulas.

When the resin (A) includes the structural unit (a4), the content ispreferably 1 to 20 mol %, more preferably 2 to 15 mol %, and still morepreferably 3 to 10 mol %, based on all structural units of the resin(A).

<Structural Unit (a5)>

Examples of a non-leaving hydrocarbon group possessed by the structuralunit (a5) include groups having a linear, branched or cyclic hydrocarbongroup. Of these, the structural unit (a5) is preferably a group havingan alicyclic hydrocarbon group.

The structural unit (a5) includes, for example, a structural unitrepresented by formula (a5-1):

wherein, in formula (a5-1).

R⁵¹ represents a hydrogen atom or a methyl group,

R⁵² represents an alicyclic hydrocarbon group having 3 to 18 carbonatoms, and a hydrogen atom included in the alicyclic hydrocarbon groupmay be substituted with an aliphatic hydrocarbon group having 1 to 8carbon atoms, and

L⁵⁵ represents a single bond or a divalent saturated hydrocarbon grouphaving 1 to 18 carbon atoms, and —CH₂— included in the saturatedhydrocarbon group may be replaced by —O— or —CO—.

The alicyclic hydrocarbon group in R⁵² may be either monocyclic orpolycyclic. The monocyclic alicyclic hydrocarbon group includes, forexample, a cyclopropyl group, a cyclobutyl group, a cyclopentyl groupand a cyclohexyl group. The polycyclic alicyclic hydrocarbon groupincludes, for example, an adamantyl group and a norbornyl group.

The aliphatic hydrocarbon group having 1 to 8 carbon atoms includes, forexample, alkyl groups such as a methyl group, an ethyl group, a propylgroup, an isopropyl group, a butyl group, a sec-butyl group, atert-butyl group, a pentyl group, a hexyl group, an octyl group and a2-ethylhexyl group.

Examples of the alicyclic hydrocarbon group having a substituentincludes a 3-methyladamantyl group and the like.

R⁵² is preferably an unsubstituted alicyclic hydrocarbon group having 3to 18 carbon atoms, and more preferably an adamantyl group, a norbornylgroup or a cyclohexyl group.

Examples of the divalent saturated hydrocarbon group in L⁵⁵ include adivalent chain saturated hydrocarbon group and a divalent alicyclicsaturated hydrocarbon group, and a divalent chain saturated hydrocarbongroup is preferable.

The divalent chain saturated hydrocarbon group includes, for example,alkanediyl groups such as a methylene group, an ethylene group, apropanediyl group, a butanediyl group and a pentanediyl group.

The divalent alicyclic saturated hydrocarbon group may be eithermonocyclic or polycyclic. Examples of the monocyclic alicyclic saturatedhydrocarbon group include cycloalkanediyl groups such as acyclopentanediyl group and a cyclohexanediyl group. Examples of thepolycyclic divalent alicyclic saturated hydrocarbon group include anadamantanediyl group and a norbornanediyl group.

The group in which —CH₂— included in the divalent saturated hydrocarbongroup represented by L⁵⁵ is replaced by —O— or —CO— includes, forexample, groups represented by formula (L1-1) to formula (L1-4). In thefollowing formulas, * and ** each represent a bonding site, andrepresents a bonding site to an oxygen atom.

In formula (L1-1),

X^(x1) represents *—O—CO— or *—CO—O— (* represents a bonding site toL^(x1)),

L^(x1) represents a divalent aliphatic saturated hydrocarbon grouphaving 1 to 16 carbon atoms,

L^(x2) represents a single bond or a divalent aliphatic saturatedhydrocarbon group having 1 to 15 carbon atoms, and

the total number of carbon atoms of L^(x1) and L^(x2) is 16 or less.

In formula (L1-2),

L^(x3) represents a divalent aliphatic saturated hydrocarbon grouphaving 1 to 17 carbon atoms,

L^(x4) represents a single bond or a divalent aliphatic saturatedhydrocarbon group having 1 to 16 carbon atoms, and

the total number of carbon atoms of L^(x3) and L^(x4) is 17 or less.

In formula. (L1-3),

L^(x5) represents a divalent aliphatic saturated hydrocarbon grouphaving 1 to 15 carbon atoms,

L^(x6) and L^(x7) each independently represent a single bond or adivalent aliphatic saturated hydrocarbon group having 1 to 14 carbonatoms, and

the total number of carbon atoms of L^(x5), L^(x6) and L^(x7) is 15 orless.

In formula. (L1-4),

L^(x8) and L^(x9) represents a single bond or a divalent aliphaticsaturated hydrocarbon group having 1 to 12 carbon atoms,

W^(x1) represents a divalent alicyclic saturated hydrocarbon grouphaving 3 to 15 carbon atoms, and

the total number of carbon atoms of L^(x8), L^(x9) and W^(x1) is 15 orless.

L^(x1) is preferably a divalent aliphatic saturated hydrocarbon grouphaving 1 to 8 carbon atoms, and more preferably a methylene group or anethylene group.

L^(x2) is preferably a single bond or a divalent aliphatic saturatedhydrocarbon group having 1 to 8 carbon atoms, and more preferably asingle bond.

L^(x3) is preferably a divalent aliphatic saturated hydrocarbon grouphaving 1 to 8 carbon atoms.

L^(x4) is preferably a single bond or a divalent aliphatic saturatedhydrocarbon group having 1 to 8 carbon atoms.

L^(x5) is preferably a divalent aliphatic saturated hydrocarbon grouphaving 1 to 8 carbon atoms, and more preferably a methylene group or anethylene group.

L^(x6) is preferably a single bond or a divalent aliphatic saturatedhydrocarbon group having 1 to 8 carbon atoms, and more preferably amethylene group or an ethylene group.

L^(x7) is preferably a single bond or a divalent aliphatic saturatedhydrocarbon group having 1 to 8 carbon atoms.

L^(x8) is preferably a single bond or a divalent aliphatic saturatedhydrocarbon group having 1 to 8 carbon atoms, and more preferably asingle bond or a methylene group.

L^(x9) is preferably a single bond or a divalent aliphatic saturatedhydrocarbon group having 1 to 8 carbon atoms, and more preferably asingle bond or a methylene group.

W^(x1) is preferably a divalent alicyclic saturated hydrocarbon grouphaving 3 to 10 carbon atoms, and more preferably a cyclohexanediyl groupor an adamantanediyl group.

The group represented by formula (L1-1) includes, for example, thefollowing divalent groups.

The group represented by formula (L1-2) includes, for example, thefollowing divalent groups.

The group represented by formula (L1-3) includes, for example, thefollowing divalent groups.

The group represented by formula (L1-4) includes, for example, thefollowing divalent groups.

L⁵⁵ is preferably a single bond or a group represented by formula(L1-1).

Examples of the structural unit (a5-1) include the following structuralunits and structural units in which a methyl group corresponding to R⁵¹in the structural unit (a5-1) in the following structural units issubstituted with a hydrogen atom.

When the resin includes the structural unit (a5), the content ispreferably 1 to 30 mol %, more preferably 2 to 20 mol %, and still morepreferably 3 to 15 mol %, based on all structural units of the resin(A).

<Structural Unit (II)>

The resin (A) may further include a structural unit which is decomposedupon exposure to radiation to generate an acid (hereinafter sometimesreferred to as “structural unit (II)). Specific examples of thestructural unit (II) include the structural units mentioned in JP2016-79235 A, and a structural unit having a sulfonate group or acarboxylate group and an organic cation in a side chain or a structuralunit having a sulfonio group and an organic anion in a side chain ispreferable.

The structural unit having a sulfonate group or a carboxylate group in aside chain is preferably a structural unit represented by formula(II-2-A′):

wherein, in formula (II-2-A′),

X^(III3) represents a divalent saturated hydrocarbon group having 1 to18 carbon atoms, —CH₂— included in the saturated hydrocarbon group maybe replaced by —O—, —S— or —CO—, and a hydrogen atom included in thesaturated hydrocarbon group may be substituted with a halogen atom, analkyl group having 1 to 6 carbon atoms which may have a halogen atom, ora hydroxy group,

A^(x1) represents an alkanediyl group having 1 to 8 carbon atoms, and ahydrogen atom included in the alkanediyl group may be substituted with afluorine atom or a perfluoroalkyl group having 1 to 6 carbon atoms,

RA⁻ represents a sulfonate group or a carboxylate group,

R^(III3) represents a hydrogen atom, a halogen atom or an alkyl grouphaving 1 to 6 carbon atoms which may have a halogen atom, and

ZA⁺ represents an organic cation.

Examples of the halogen atom represented by R^(III3) include a fluorineatom, a chlorine atom, a bromine atom and an iodine atom.

Examples of the alkyl group having 1 to 6 carbon atoms which may have ahalogen atom represented by R^(III3) include those which are the same asthe alkyl group having 1 to 6 carbon atoms which may have a halogen atomrepresented by R^(a8).

Examples of the alkanediyl group having 1 to 8 carbon atoms representedby A^(x1) include a methylene group, an ethylene group, apropane-1,3-diyl group, a butane-1,4-diyl group, a pentane-1,5-diylgroup, a hexane-1,6-diyl group, an ethane-1,1-diyl group, apropane-1,1-diyl group, a propane-1,2-diyl group, a propane-2,2-diylgroup, a pentane-2,4-diyl group, a 2-methylpropane-1,3-diyl group, a2-methylpropane-1,2-diyl group, a pentane-1,4-diyl group, a2-methylbutane-1,4-diyl group and the like.

Examples of the perfluoroalkyl group having 1 to 6 carbon atoms whichmay be substituted in A^(x1) include a trifluoromethyl group, aperfluoroethyl group, a perfluoropropyl group, a perfluoroisopropylgroup, a perfluorobutyl group, a perfluorosec-butyl group, aperfluorotert-butyl group, a perfluoropentyl group, a perfluorohexylgroup and the like.

Examples of the divalent saturated hydrocarbon group having 1 to 18carbon atoms represented by X^(III3) include a linear or branchedalkanediyl group, a monocyclic or a polycyclic divalent alicyclicsaturated hydrocarbon group, or a combination thereof.

Specific examples thereof include linear alkanediyl groups such as amethylene group, an ethylene group, a propane-1,3-diyl group, apropane-1,2-diyl group, a butane-1,4-diyl group, a pentane-1,5-diylgroup, a hexane-1,6-diyl group, a heptane-1,7-diyl group, anoctane-1,8-diva group, a nonane-1,9-diyl group, a decane-1,10-diylgroup, an undecane-1,11-diyl group and a dodecane-1,12-diyl group;branched alkanediyl groups such as a butane-1,3-diyl group, a2-methylpropane-1,3-diyl group, a 2-methylpropane-1,2-diyl group, apentane-1,4-diyl group and a 2-methylbutane-1,4-diyl group;cycloalkanediyl groups such as a cyclobutane-1,3-diyl group, acyclopentane-1,3-diyl group, a cyclohexane-1,4-diyl group and acyclooctane-1,5-diyl group; and divalent polycyclic alicyclic saturatedhydrocarbon groups such as a norbornane-1,4-diyl group, anorbornane-2,5-diyl group, an adamantane-1,5-diyl group and anadamantane-2,6-diyl group.

Those in which —CH₂— included in the saturated hydrocarbon group isreplaced by —O—, —S— or —CO— include, for example, divalent groupsrepresented by formula (X1) to formula (X53). Before replacing —CH₂—included in the saturated hydrocarbon group by —O—, —S— or —CO—, thenumber of carbon atoms is 17 or less. In the following formulas, * and** represent a bonding site, and * represents a bonding site to A^(x1).

X³ represents a divalent saturated hydrocarbon group having 1 to 16carbon atoms.

X⁴ represents a divalent saturated hydrocarbon group having 1 to 15carbon atoms.

X³ represents a divalent saturated hydrocarbon group having 1 to 13carbon atoms.

X⁶ represents a divalent saturated hydrocarbon group having 1 to 14carbon atoms.

X⁷ represents a divalent saturated hydrocarbon group having 1 to 14carbon atoms.

X⁸ represents a divalent saturated hydrocarbon group having 1 to 13carbon atoms.

Examples of the organic cation represented by ZA⁺ in formula (II-2-A′)include those which are the same as the cation Z in a salt representedby formula (B1).

The structural unit represented by formula (II-2-A′) is preferably astructural unit represented by formula (II-2-A):

wherein, in formula (II-2-A), R^(III3), X^(III3) and ZA⁺ are the same asdefined above,

z2A represents an integer of 0 to 6,

R^(III2) and R^(III4) each independently represent a hydrogen atom, afluorine atom or a perfluoroalkyl group having 1 to 6 carbon atoms, andwhen z2A is 2 or more, a plurality of R^(III2) and R^(IIII4) may be thesame or different from each other, and

Q^(a) and Q^(b) each independently represent a fluorine atom or aperfluoroalkyl group having 1 to 6 carbon atoms.

Examples of the perfluoroalkyl group having 1 to 6 carbon atomsrepresented by R^(III2), R^(III4), Q^(a) and Q^(b) include those whichare the same as the perfluoroalkyl group having 1 to 6 carbon atomsrepresented by the above-mentioned Q^(b1).

The structural unit represented by formula (II-2-A) is preferably astructural unit represented by formula (11-2-A-1):

wherein, in formula (II-2-A-1),

R^(III2), R^(III3), R^(III4), Q^(a), Q^(b) and ZA⁺ are the same asdefined above,

R^(III5) represents a saturated hydrocarbon group having 1 to 12 carbonatoms,

z2A1 represents an integer of 0 to 6, and

X^(I2) represents a divalent saturated hydrocarbon group having 1 to 11carbon atoms, —CH₂— included in the saturated hydrocarbon group may bereplaced by —O—, —S— or —CO—, and a hydrogen atom included in thesaturated hydrocarbon group may be substituted with a halogen atom or ahydroxy group.

Examples of the saturated hydrocarbon group having 1 to 12 carbon atomsrepresented by R^(III5) include linear or branched alkyl groups such asa methyl group, an ethyl group, a propyl group, an isopropyl group, abutyl group, a sec-butyl group, a tert-butyl group, a pentyl group, ahexyl group, a heptyl group, an octyl group, a nonyl group, a decylgroup, an undecyl group and a dodecyl group.

Examples of the divalent saturated hydrocarbon group represented byX^(I2) include those which are the same as the divalent saturatedhydrocarbon group represented by X^(III3).

The structural unit represented by formula (II-2-A-1) is more preferablya structural unit represented by formula (II-2-A-2):

wherein, in formula (II-2-A-2), R^(III3), R^(III3) and ZA⁺ are the sameas defined above, and

m and n each independently represent 1 or 2.

The structural unit represented by formula (II-2-A′) includes, forexample, the following structural units, structural units in which agroup corresponding to a methyl group for R^(III3) is substituted with ahydrogen atom, a halogen atom (e.g., a fluorine atom) or as alkyl grouphaving 1 to 6 carbon atoms which may have a halogen atom (e.g., atrifluoromethyl group, etc.) and the structural units mentioned in WO2012/050015 A. ZA⁺ represents an organic cation.

The structural unit having a sulfonio group and an organic anion in aside chain is preferably a structural unit represented by formula(II-1-1):

wherein, in formula (II-1-1),

A^(II1) represents a single bond or a divalent linking group,

R^(II1) represents a divalent aromatic hydrocarbon group having 6 to 18carbon atoms,

R^(II2) and R^(II3) each independently represent a hydrocarbon grouphaving 1 to 18 carbon atoms, and R^(II2) and R^(II3) may be bonded eachother to form a ring together with sulfur atoms to which R^(II2) andR^(II3) are bonded,

R^(II4) represents a hydrogen atom, a halogen atom or an alkyl grouphaving 1 to 6 carbon atoms which may have a halogen atom, and

A⁻ represents an organic anion.

Examples of the divalent aromatic hydrocarbon group having 6 to 18carbon atoms represented by include a phenylene group and a naphthylenegroup.

Examples of the hydrocarbon group represented by R^(II2) and R^(II3)include an alkyl group, an alicyclic hydrocarbon group, an aromatichydrocarbon group, and groups formed by combining these groups.

Examples of the halogen atom represented by include a fluorine atom, achlorine atom, a bromine atom and an iodine atom.

Examples of the alkyl group having 1 to 6 carbon atoms which may have ahalogen atom represented by include those which are the same as thealkyl group having 1 to 6 carbon atoms which may nave a halogen atomrepresented by R^(a8).

The divalent linking group represented by A^(II1) includes, for example,a divalent saturated hydrocarbon group having 1 to 18 carbon atoms, and—CH₂— included in the divalent saturated hydrocarbon group may bereplaced by —O—, —S— or —CO—. Specific examples thereof include thosewhich are the same as the divalent saturated hydrocarbon group having 1to 18 carbon atoms represented by X^(III3).

Examples of the structural unit including a cation in formula (II-1-1)include the following structural units and structural units in which agroup corresponding to a methyl group for R^(II4) is substituted with ahydrogen atom, a fluorine atom, a trifluoromethyl or the like.

Examples of the organic anion represented by A⁻ include a sulfonic acidanion, a sulfonylimide anion, a sulfonylmethide anion and a carboxylicacid anion. The organic anion represented by A⁻ is preferably a sulfonicacid anion, and the sulfonic acid anion is more preferably an anionincluded in the above-mentioned salt represented by formula (B1).

Examples of the sulfonylimide anion represented by A⁻ include thefollowings.

Examples of the sulfonylmethide anion include the followings.

Examples of the carboxylic acid anion include the followings.

Examples of the structural unit represented by formula (II-1-1) includethe following structural units.

When the structural unit (II) is included in the resin (A), the contentof the structural unit (II) is preferably 1 to 20 mol %, more preferably2 to 15 mol %, and still more preferably 3 to 10 mol %, based on allstructural units of the resin (A).

The resin (A.) may include structural units other than the structuralunits mentioned above, and examples of such structural unit includestructural units well-known in the art.

The resin (A) is preferably a resin composed of a structural unit (I)and a structural unit (a1-5), a resin composed of a structural unit (I),a structural unit (a1-5), a structural unit (a1-1) and a structuralunit. (a1-2), a resin composed of a structural unit (I) , a structuralunit (a1-5) and a structural unit (a1-1), a resin composed of astructural unit (I), a structural unit (a1-5) and a structural unit(a1-2) , a resin composed of a structural unit (I), a structural unit(a1-5), a structural unit (a1-1), a structural unit (a1-2) and astructural unit (s) , a resin composed of a structural unit (I), astructural unit (a1-5), a structural unit (a1-1) and a structural unit(s), a resin composed of a structural unit (I), a structural unit(a1-5), a structural unit (a1-2) and a structural unit (s) , a resincomposed of a structural unit (I), a structural unit (a1-5) and astructural unit (s), a resin composed of a structural unit (I), astructural unit (a1-5), a structural unit (a1-1), a structural unit(a1-2), a structural unit (s), a structural unit (a4) and/or astructural unit (a5) , or a resin composed only of a structural unit(I), a structural unit (a1-5) , a structural unit (a1-1) , a structuralunit (a1-2) and a structural unit (a4) , and more preferably a resincomposed of a structural unit (I) and a structural unit (a1-5) , a resincomposed of a structural unit (I) , a structural unit (a1-5), astructural unit (a1-1) and a structural unit (a1-2) , a resin composedof a structural unit (I) , a structural unit (a1-5) and a structuralunit (a1-1), a resin composed of a structural unit (I) , a structuralunit (a1-5) and a structural unit (a1-2) , a resin composed of astructural unit (I), a structural unit (a1-5), a structural unit (a1-1),a structural unit (a1-2) and a structural unit (s) , a resin composed ofa structural unit (I) , a structural unit (a1-5), a structural unit(a1-1) and a structural unit (s) , a resin composed of a structural unit(I) , a structural unit (a1-5), a structural unit (a1-2) and astructural unit (s) , or a resin composed of a structural unit (I), astructural unit (a1-5) and a structural unit (s).

The structural unit (s) is preferably at least one selected from thegroup consisting of a structural unit (a2) and a structural unit (a3).The structural unit (a2) is preferably a structural unit represented byformula (a2-A) or a structural unit represented by formula (a2-1). Thestructural unit (a3) is preferably at least one selected from the groupconsisting of a structural unit represented by formula (a3-1), astructural unit represented by formula (a3-2) and a structural unitrepresented by formula (a3-4).

The respective structural units constituting the resin may be usedalone, or two or more structural units may be used in combination. Usinga monomer from which these structural units are derived, it is possibleto produce by a known polymerization method (e.g., radicalpolymerization method). The content of the respective structural unitsincluded in the resin (A) can be adjusted according to the amount of themonomer used in the polymerization.

The weight-average molecular weight of the resin (A) is preferably 2,000or more (more preferably 2,500 or more, and still more preferably 3,000or more), and 50,000 or less (more preferably 30,000 or less, and stillmore preferably 15,000 or less).

As used herein, the weight-average molecular weight is a valuedetermined by gel permeation chromatography. Gel permeationchromatography can be measured under the analysis conditions mentionedin Examples

[Resist Composition]

The resist composition of the present invention. includes a resin and anacid generator (hereinafter sometimes referred to as “acid generator(B)”).

Examples of the acid generator include acid generators known in theresist field.

The resist composition of the present invention may further include theresin other than the resin (A).

The resist composition of the present invention preferably includes aquencher such as a salt generating an acid having an acidity lower thanthat of an acid generated from an acid generator (hereinafter sometimesreferred to as “quencher (C)”), and preferably includes a solvent.(hereinafter sometimes referred to as “solvent (E)”.

<Resin other than Resin (A)>

In the resist composition of the present invention, resin other than theresin (A) may be used in combination. The resin other than the resin (A)may be a resin which does not include at least one of a structural unit(I) and a structural unit (a1-5). Examples of the resin include a resinin which the structural unit (I) is removed from the resin (A)(hereinafter sometimes referred to as “resin (AY)”), a resin in whichthe structural unit (a1-5) is removed from the resin (A) (hereinaftersometimes referred to as “resin. (AZ)”), a resin composed only of astructural unit (a4) and a structural unit (a5) (hereinafter sometimesreferred to as resin (X)) and the like.

Particularly, the resin (X) is preferably a resin including a structuralunit (a4).

In the resin (X), the content of the structural unit (a4) is preferably30 mol % or more, more preferably 40 mol % or more, and still morepreferably 45 mol % or more, based on the total of all structural unitsof the resin (X).

Examples of the structural unit, which may be further included in theresin (X) , include a structural unit (a2) , a structural unit (a3) andstructural units derived from other known monomers. Particularly, theresin (X) is preferably a resin composed only of a structural unit (a4)and/or a structural unit (a5).

The respective structural units constituting the resin (X) may be usedalone, or two or more structural units may be used in combination. Usinga monomer from which these structural units are derived, it is possibleto produce by a known polymerization method (e.g., radicalpolymerization method). The content of the respective structural unitsincluded in the resin (X) can be adjusted according to the amount of themonomer used in the polymerization.

Each weight-average molecular weight of the resin (AY), the resin (AZ)and the resin (X) is preferably 6,000 or more (more preferably 7,000 ormore) and 80,000 or less (more preferably 60,000 or less). Themeasurement means of the weight-average molecular weight of the resin(AY) , the resin (AZ) and the resin (X) is the same as in the case ofthe resin (A).

When the resist composition of the present invention includes the resin(AY) and/or the resin (AZ), the total content is usually 1 to 2,500parts by mass (more preferably 10 to 1,000 parts by mass) based on 100parts by mass of the resin (A).

When the resist composition includes the resin (X), the content ispreferably 1 to 60 parts by mass, more preferably 1 to 50 parts by mass,still more preferably 1 to 40 parts by mass, particularly preferably 1to 30 parts by mass, and particularly preferably 1 to 8 parts by mass,based on 100 parts by mass of the resin (A).

The content of the resin (A) in the resist composition is preferably 80%by mass or more and 99% by mass or less, and more preferably 90% by massor more 99% by mass or less, based on the solid component of the resistcomposition. When including the resin other than the resin (A) , thetotal content of the resin (A) and the resin other than the resin (A) ispreferably 80% by mass or more and 99% by mass or less, and morepreferably 90% by mass or more 99% by mass or less, based on the solidcomponent of the resist composition. The solid component of the resistcomposition and the content of the resin thereto can be measured by aknown analysis means such as liquid chromatography or gaschromatography.

<Acid Generator (B)>

Either nonionic or ionic acid generator may be used as the acidgenerator (B). Examples of the nonionic acid generator include sulfonateesters (e.g., 2-nitrobenzyl ester, aromatic sulfonate, oxime sulfonate,N-sulfonyloxyimide, sulfonyloxyketone, diazonaphthoquinone 4-sulfonate),sulfones (e.g., disulfone, ketosulfone, sulfonyldiazomethane) and thelike. Typical examples of the ionic acid generator include onium saltscontaining an onium cation. (e.g., diazonium salt, phosphonium salt,sulfonium salt, iodonium salt). Examples of the anion of the onium saltinclude sulfonic acid anion, sulfonylimide anion, sulfonylmethide anionand the like.

It is possible to use, as the acid generator (B), compounds generatingan acid upon exposure to radiation mentioned in. JP 63-26653 A, JP55-164824 A, JP 62-69263 A, JP 63-146038 A, JP 63-163452 A, JP 62-153853A, JP 63-146029 A, U.S. Pat. Nos. 3,779,778, 3,849,137, DE Patent No.3914407 and EP Patent No. 126,712. Compounds produced by a known methodmay also be used. Two or more acid generators (B) may also be used incombination.

The acid generator (B) is preferably a fluorine-containing acidgenerator, and more preferably a salt represented by formula (B1)(hereinafter sometimes referred to as “acid generator (B1)”):

wherein, in formula (B1),

Q^(b1) and Q^(b2) each independently represent a fluorine atom or aperfluoroalkyl group having 1 to 6 carbon atoms,

L^(b1) represents a divalent saturated hydrocarbon group having 1 to 24carbon atoms, —CH₂— included in the divalent saturated hydrocarbon groupmay be replaced by —O— or —CO—, and a hydrogen atom included in thedivalent saturated hydrocarbon group may be substituted with a fluorineatom or a hydroxy group,

Y represents a methyl group which may have a substituent or an alicyclichydrocarbon group having 3 to 18 carbon atoms which may have asubstituent, and —CH₂— included in the alicyclic hydrocarbon group maybe replaced by —O—, —S(O)₂— or —CO—, and

Z⁺ represents an organic cation.

Examples of the perfluoroalkyl group represented by Q^(b1) and Q^(b2)include a trifluoromethyl group, a perfluoroethyl group, aperfluoropropyl group, a perfluoroisopropyl group, a perfluorobutylgroup, a perfluorosec-butyl group, a perfluorotert-butyl group, aperfluoropentyl group and a perfluorohexyl group.

Preferably, Q^(b1) and Q^(b2) are each independently a fluorine atom ora trifluoromethyl group, and more preferably, both are fluorine atoms.

Examples of the divalent saturated hydrocarbon group in L^(b1) include alinear alkanediyl group, a branched alkanediyl group, and a monocyclicor polycyclic divalent alicyclic saturated hydrocarbon group, or thedivalent saturated hydrocarbon group may be a group formed by using twoor more of these groups in combination.

Specific examples thereof include linear alkanediyl groups such as amethylene group, an ethylene group, a propane-1,3-diyl group, abutane-1,4-diyl group, a pentane-1,5-diyl group, a hexane-1,6-diylgroup, a heptane-1,7-diyl group, an octane-1,8-diyl group, anonane-1,9-diyl group, a decane-1,10-diyl group, an undecane-1,11-diylgroup, a dodecane-1,12-diyl group, a tridecane-1,13-diyl group, atetradecane-1,14-diyl group, a pentadecane-1,15-diyl group, ahexadecane-1,16-diyl group and a heptadecane-1,17-diyl group;

branched alkanediyl groups such as an ethane-1,1-diyl group, apropane-1,1-group, a propane-1,2-diyl group, a propane-2,2-diyl group, apentane-2,4-diyl group, a 2-methylpropane-1,3-diyl group, a2-methylpropane-1,2-diyl group, a pentane-1,4-diyl group and a2-methylbutane-1,4-diyl group;

monocyclic divalent alicyclic saturated hydrocarbon groups which arecycloalkanediyl groups such as a cyclobutane-1,3-diyl group, acyclopentane-1,3-diyl group, a cyclohexane-1,4-diyl group and acyclooctane-1,5-diyl group; and

polycyclic divalent alicyclic saturated hydrocarbon groups such as anorbornane-1,4-diyl group, a norbornane-2,5-diyl group, anadamantane-1,5-diyl group and an adamantane-2,6-diyl group.

The group in which —CH₂— included in the divalent saturated hydrocarbongroup represented by L^(b1) is replaced by —O— or —CO— includes, forexample, a group represented by any one of formula (b1-1) to formula(b1-3). In groups represented by formula (b1-1) to formula (b1-3) andgroups represented by formula (b1-4) to formula (b1-11) which arespecific examples thereof, * and ** represent a bonding site, and *represents a bonding site to —Y.

In formula (b1-1),

L^(b2) represents a single bond or a divalent saturated hydrocarbongroup having 1 to 22 carbon atoms, and a hydrogen atom included in thesaturated hydrocarbon group may be substituted with a fluorine atom,

L^(b3) represents a single bond or a divalent saturated hydrocarbongroup having 1 to 22 carbon atoms, a hydrogen atom included in thesaturated hydrocarbon group may be substituted with a fluorine atom or ahydroxy group, and —CH₂— included in the saturated hydrocarbon group maybe replaced by —O— or —CO—, and

the total number of carbon atoms of L^(b2) and L^(b3) is 22 or less.

In formula (b1-2),

L^(b4) represents a single bond or a divalent saturated hydrocarbongroup having 1 to 22 carbon atoms, and a hydrogen atom included in thesaturated hydrocarbon group may be substituted with a fluorine atom,

L^(b5) represents a single bond or a divalent saturated hydrocarbongroup having 1 to 22 carbon atoms, a hydrogen atom included in thesaturated hydrocarbon group may be substituted with a fluorine atom or ahydroxy group, and —CH₂— included in the saturated hydrocarbon group maybe replaced by —O— or —CO—, and

the total number of carbon atoms of L^(b4) and L^(b5) is 22 or less.

In formula (b1-3),

L^(b6) represents a single bond or a divalent saturated hydrocarbongroup having 1 to 23 carbon atoms, and a hydrogen atom included in thesaturated hydrocarbon group may be substituted with a fluorine atom or ahydroxy group,

L^(b7) represents a single bond or a divalent saturated hydrocarbongroup having 1 to 23 carbon atoms, a hydrogen atom included in thesaturated hydrocarbon group may be substituted with a fluorine atom or ahydroxy group, and —CH₂— included in the saturated hydrocarbon group maybe replaced by —O— or —CO—, and

the total number of carbon atoms of L^(b6), and L^(b7) is 23 or less.

In groups represented by formula (b1-1) to formula (b1-3) , when —CH₂—included in the saturated hydrocarbon group is replaced by —O— or —CO—,the number of carbon atoms before replacement is taken as the number ofcarbon atoms of the saturated hydrocarbon group.

Examples of the divalent saturated hydrocarbon group include those whichare the same as the divalent saturated hydrocarbon group for L^(b1).

L^(b2) is preferably a single bond.

L^(b3) is preferably a divalent saturated hydrocarbon group having 1 to4 carbon atoms.

L^(b4) is preferably a divalent saturated hydrocarbon group having 1 to8 carbon atoms, and a hydrogen atom included in the divalent saturatedhydrocarbon group may be substituted with a fluorine atom.

L^(b5) is preferably a single bond or a divalent saturated hydrocarbongroup having 1 to 8 carbon atoms.

L^(b6) is preferably a single bond or a divalent saturated hydrocarbongroup having 1 to 4 carbon atoms, and a hydrogen atom included in thesaturated hydrocarbon group may be substituted with a fluorine atom.

L^(b7) is preferably a single bond or a divalent saturated hydrocarbongroup having 1 to 18 carbon atoms, a hydrogen atom included in thesaturated hydrocarbon group may be substituted with a fluorine atom or ahydroxy group, and —CH₂— included in the divalent saturated hydrocarbongroup may be replaced by —O— or —CO—.

The group in which —CH₂— included in the divalent saturated hydrocarbongroup represented by L^(b1) is replaced by —O— or —CO— is preferably agroup represented by formula (b1-1) or formula (b1-3).

Examples of the group represented by formula (b1-1) include groupsrepresented by formula (b1-4) to formula (b1-8).

In formula (b1-4),

L^(b8) represents a single bond or a divalent saturated hydrocarbongroup having 1 to 22 carbon atoms, and a hydrogen atom included in thesaturated hydrocarbon group may be substituted with a fluorine atom or ahydroxy group.

In formula (b1-5),

L^(b9) represents a divalent saturated hydrocarbon group having 1 to 20carbon atoms, and —CH₂— included in the divalent saturated hydrocarbongroup may be replaced by —O— or —CO—,

L^(b10) represents a single bond or a divalent saturated hydrocarbongroup having 1 to 19 carbon atoms, and a hydrogen atom included in thedivalent saturated hydrocarbon group may be substituted with a fluorineatom or a hydroxy group, and

the total number of carbon atoms of L^(b9) and L^(b0) is 20 or less.

In formula (b1-6),

L^(b11) represents a divalent saturated hydrocarbon group having 1 to 21carbon atoms,

L^(b12) represents a single bond or a divalent saturated hydrocarbongroup having 1 to 20 carbon atoms, and a hydrogen atom included in thedivalent saturated hydrocarbon group may be substituted with a fluorineatom or a hydroxy group, and

the total number of carbon atom of L^(b11) and L^(b12) is 21 or less.

In formula (b1-7),

L^(b13) represents a divalent saturated hydrocarbon group having 1 to 19carbon atoms,

L^(b14) represents a single bond or a divalent saturated hydrocarbongroup having 1 to 18 carbon atoms, and —CH₂— included in the divalentsaturated hydrocarbon group may be replaced by —O— or —CO—,

L^(b15) represents a single bond or a divalent saturated hydrocarbongroup having 1 to 18 carbon atoms, and a hydrogen atom included in thedivalent saturated hydrocarbon group may be substituted with a fluorineatom or a hydroxy group, and

the total number of carbon atoms of L^(b13) to L^(b15) is 19 or less.

In formula (b¹⁻8),

L^(b16) represents a divalent saturated hydrocarbon group having 1 to 18carbon atoms, and —CH₂— included in the divalent saturated hydrocarbongroup may be replaced by —O— or —CO—,

L^(b17) represents a divalent saturated hydrocarbon group having 1 to 18carbon atoms,

L^(b18) represents a single bond or a divalent saturated hydrocarbongroup having 1 to 17 carbon atoms, and a hydrogen atom included in thedivalent saturated hydrocarbon group may be substituted with a fluorineatom or a hydroxy group, and

the total number of carbon atoms of L^(b16) to L^(b18) is 19 or less.

L^(b8) is preferably a divalent saturated hydrocarbon group having 1 to4 carbon atoms.

L^(b9) is preferably a divalent saturated hydrocarbon group having 1 to8 carbon atoms.

L^(b10) is preferably a single bond or a divalent saturated hydrocarbongroup having 1 to 19 carbon atoms, and more preferably a single bond ora divalent saturated hydrocarbon group having 1 to 8 carbon atoms.

L^(b11) is preferably a divalent saturated hydrocarbon group having 1 to8 carbon atoms.

L^(b12) is preferably a single bond or a divalent saturated hydrocarbongroup having 1 to 8 carbon atoms.

L^(b13) is preferably a divalent saturated hydrocarbon group having 1 to12 carbon atoms.

L^(b14) is preferably a single bond or a divalent saturated hydrocarbongroup having 1 to 6 carbon atoms.

L^(b15) is preferably a single bond or a divalent saturated hydrocarbongroup having 1 to 18 carbon atoms, and more preferably a single bond ora divalent saturated hydrocarbon group having 1 to 8 carbon atoms.

L^(b16) is preferably a divalent saturated hydrocarbon group having 1 to12 carbon atoms.

L^(b17) is preferably a divalent saturated hydrocarbon group having 1 to6 carbon atoms.

L^(b18) is preferably a single bond or a divalent saturated hydrocarbongroup having 1 to 17 carbon atoms, and more preferably a single bond ora divalent saturated hydrocarbon group having 1 to 4 carbon atoms.

Examples of the group represented by formula (b1-3) include groupsrepresented by formula (b1-9) to formula (b1-11).

In formula (b1-9),

L^(b19) represents a single bond or a divalent saturated hydrocarbongroup having 1 to 23 carbon atoms, and a hydrogen atom included in thesaturated hydrocarbon group may be substituted with a fluorine atom,

L^(b20) represents a single bond or a divalent saturated hydrocarbongroup having 1 to 23 carbon atoms, and a hydrogen atom included in thesaturated hydrocarbon group may be substituted with a fluorine atom, ahydroxy group or an alkylcarbonyloxy group, —CH₂— included in thealkylcarbonyloxy group may be replaced by —O— or —CO—, and a hydrogenatom included in the alkylcarbonyloxy group may be substituted with ahydroxy group, and

the total number of carbon atoms of L^(b19) and L^(b20) is 23 or less.

In formula (b1-10),

L^(b21) represents a single bond or a divalent saturated hydrocarbongroup having 1 to 21 carbon atoms, and a hydrogen atom included in thesaturated hydrocarbon group may be substituted with a fluorine atom,

L^(b22) represents a single bond or a divalent saturated hydrocarbongroup having 1 to 21 carbon atoms,

L^(b23) represents a single bond or a divalent saturated hydrocarbongroup having 1 to 21 carbon atoms, a hydrogen atom included in thesaturated hydrocarbon group may be substituted with a fluorine atom, ahydroxy group or an alkylcarbonyloxy group, —CH₂— included in thealkylcarbonyloxy group may be replaced by —O— or —CO—, and a hydrogenatom included in the alkylcarbonyloxy group may be substituted with ahydroxy group, and

the total number of carbon atoms of L^(b21), L^(b22) and L^(b23) is 21or less.

In formula (b1-11),

L^(b24) represents a single bond or a divalent saturated hydrocarbongroup having 1 to 20 carbon atoms, and a hydrogen atom included in thesaturated hydrocarbon group may be substituted with a fluorine atom,

L^(b23) represents a divalent saturated hydrocarbon group having 1 to 21carbon atoms,

L^(b26) represents a single bond or a divalent saturated hydrocarbongroup having 1 to 20 carbon atoms, a hydrogen atom included in thesaturated hydrocarbon group may be substituted with a fluorine atom, ahydroxy group or an alkylcarbonyloxy group, —CH₂— included in thealkylcarbonyloxy group may be replaced by —O— or —CO—, and a hydrogenatom included in the alkylcarbonyloxy group may be substituted with ahydroxy group, and

the total number of carbon atoms of L^(b24), L^(b25) and L^(b26) is 21or less.

In groups represented by formula (b1-9) to formula. (b1-11), when ahydrogen atom included in the saturated hydrocarbon group is substitutedwith an alkylcarbonyloxy group, the number of carbon atoms beforesubstitution is taken as the number of carbon atoms of the saturatedhydrocarbon group.

Examples of the alkylcarbonyloxy group include an acetyloxy group, apropionyloxy group, a butyryloxy group, a cyclohexylcarbonyloxy group,an adamantylcarbonyloxy group and the like.

Examples of the group represented by formula (b1-4) include thefollowings:

Examples of the group represented by formula (b1-5) include thefollowings:

Examples of the group represented by formula (b1-6) include thefollowings:

Examples of the group represented by formula (b1-7) include thefollowings:

Examples of the group represented by formula (b1-8) include thefollowings:

Examples of the group represented by formula (b1-2) include thefollowings:

Examples of the group represented by formula (b1-9) include thefollowings:

Examples of the group represented by formula (b1-10) include thefollowings:

Examples of the group represented by formula (b1-11) include thefollowings:

Examples of the alicyclic hydrocarbon group represented by Y includegroups represented by formula (Y1) to formula (Y11) and formula (Y36) toformula (Y38).

When —CH₂— included in the alicyclic hydrocarbon group represented by Yis replaced by —O—, —S(O)₂— or —CO—, the number may be 1, or 2 or more.Examples of such group include groups represented by formula (Y12) toformula (Y35) and formula (Y39) to formula (Y41).

The alicyclic hydrocarbon group represented by Y is preferably a grouprepresented by any one of formula (Y1) to formula (Y20), formula (Y26),formula (Y27), formula (Y30), formula (Y31) and formula (Y39) to formula(Y41), more preferably a group represented by formula (Y11), formula(Y15), formula (Y16), formula (Y20) , formula (Y26) , formula (Y27),formula (Y30) , formula (Y31), formula (Y39) or formula (Y40), and stillmore preferably a group represented by formula (Y11), formula (Y15) ,formula (Y20) , formula (Y26), formula (Y27), formula (Y30) , formula(Y31), formula (Y39) or formula (Y40).

When the alicyclic hydrocarbon group represented by Y is a spiro ringcontaining an oxygen atom, such as formula (Y28) to formula (Y35) andformula (Y39) to formula (Y40), the alkanediyl group between two oxygenatoms preferably includes one or more fluorine atoms. Of alkanediylgroups included in a ketal structure, it is preferable that a methylenegroup adjacent to the oxygen atom is not substituted with a fluorineatom.

Examples of the substituent of the methyl group represented by Y includea halogen atom, a hydroxy group, an alicyclic hydrocarbon group having 3to 16 carbon atoms, an aromatic hydrocarbon group having 6 to 18 carbonatoms, a glycidyloxy group, a —(CH₂)_(ja)—CO—O—R^(b1) group or a—(CH₂)_(ja)—O—CO—R^(b1) group (wherein R^(b1) represents an alkyl grouphaving 1 to 16 carbon atoms, an alicyclic hydrocarbon group having 3 to16 carbon atoms, an aromatic hydrocarbon group having 6 to 18 carbonatoms or groups obtained by combining these groups, ja represents aninteger of 0 to 4, and —CH₂— included in the alkyl group and thealicyclic hydrocarbon group may be replaced by —O—, —SO₂— or —CO—, ahydrogen atom included in the alkyl group, the alicyclic hydrocarbongroup and the aromatic hydrocarbon group may be substituted with ahydroxy group or a fluorine atom) and the like.

Examples of the substituent of the alicyclic hydrocarbon grouprepresented by Y include a halogen atom, a hydroxy group, an alkyl grouphaving 1 to 12 carbon atoms which may be substituted with a hydroxygroup, an alicyclic hydrocarbon group having 3 to 16 carbon atoms, analkoxy group having 1 to 12 carbon atoms, an aromatic hydrocarbon grouphaving 6 to 18 carbon atoms, an aralkyl group having 7 to 21 carbonatoms, an alkylcarbonyl group having 2 to 4 carbon atoms, a glycidyloxygroup, a —(CH₂)_(ja)—CO—O—R^(b1) group or a —(CH₂)_(ja)—O—CO—R^(b1)group (wherein R^(b1) represents an alkyl group having 1 to 16 carbonatoms, an alicyclic hydrocarbon group having 3 to 16 carbon atoms, anaromatic hydrocarbon group having 6 to 18 carbon atoms or groupsobtained by combining these groups, ja represents an integer of 0 to 4,and —CH₂— included in the alkyl group and the alicyclic hydrocarbongroup may be replaced by —O—, —S(O)₂— or —CO—, a hydrogen atom includedin the alkyl group, the alicyclic hydrocarbon group and the aromatichydrocarbon group may be substituted with a hydroxy group or a fluorineatom) and the like.

Examples of the halogen atom include a fluorine atom, a chlorine atom, abromine atom and an iodine atom.

Examples of the alicyclic hydrocarbon group include a cyclopentyl group,a cyclohexyl group, a methylcyclohexyl group, a dimethylcyclohexylgroup, a cycloheptyl group, a cyclooctyl group, a norbornyl group, anadamantyl group and the like.

Examples of the aromatic hydrocarbon group include aryl groups such as aphenyl group, a naphthyl group, an anthryl group, a biphenyl group and aphenanthryl group. The aromatic hydrocarbon group may have a chainhydrocarbon group or an alicyclic hydrocarbon group, and examples of thearomatic hydrocarbon group having a chain hydrocarbon group include atolyl group, a xylyl group, a cumenyl group, a mesityl group, ap-ethylphenyl group, a p-tert-butylphenyl group, a 2,6-diethylphenylgroup, a 2-methyl-6-ethylphenyl group and the like, and examples of thearomatic hydrocarbon. group having an alicyclic hydrocarbon groupinclude a p-cyclohexylphenyl group, a p-adamantylphenyl group and thelike.

Examples of the alkyl group include a methyl group, an ethyl group, apropyl group, an isopropyl group, a butyl group, a sec-butyl group, atert-butyl group, a pentyl group, a hexyl group, a heptyl group, a2-ethylhexyl group, an octyl group, a nonyl group, a decyl group, anundecyl group, a dodecyl group and the like.

Examples of the alkyl group substituted with a hydroxy group includehydroxyalkyl groups such as a hydroxymethyl group and a hydroxyethylgroup.

Examples of the alkoxy group include a methoxy group, an ethoxy group, apropoxy group, a butoxy group, a pentyloxy group, a hexyloxy group, aheptyloxy group, an octyloxy group, a decyloxy group and a dodecyloxygroup.

Examples of the aralkyl group include a benzyl group, a phenethyl group,a phenylpropyl group, a naphthylmethyl group and a naphthylethyl group.

Examples of the alkylcarbonyl group include an acetyl group, a propionylgroup and a butyryl group.

Examples of Y include the followings.

Y is preferably an alicyclic hydrocarbon group having 3 to 18 carbonatoms which may have a substituent, more preferably an adamantyl groupwhich may have a substituent, and —CH₂— constituting the alicyclichydrocarbon group or the adamantyl group may be replaced by —CO—,—S(O)₂— or —CO—. Y is still more preferably an adamantyl group, ahydroxyadamantyl group, an oxoadamantyl group, or groups represented bythe followings.

The anion in the salt represented by (B1) is preferably anionsrepresented by formula (B1-A-1) to formula (B1-A-55) [hereinaftersometimes referred to as “anion (B1-A-1)” according to the number offormula], and more preferably an anion represented by any one of formula(B1-A-1) to formula (B1-A-4), formula (Bl-A-9), formula (B1-A-10),formula (B1-A-24) to formula (B1-A-33), formula (B1-A-36) to formula(B1-A-40) and formula (B1-A-47) to formula (B1-A-55).

R^(i2) to R^(i7) each independently represent, for example, an alkylgroup having 1 to 4 carbon atoms, and preferably a methyl group or anethyl group. R^(i8) is, for example, an chain hydrocarbon group having 1to 12 carbon atoms, preferably an alkyl group having 1 to 4 carbonatoms, an alicyclic hydrocarbon group having 5 to 12 carbon atoms orgroups formed by combining these groups, and more preferably a methylgroup, an ethyl group, a cyclohexyl group or an adamantyl group. L^(A41)is a single bond or an alkanediyl group having 1 to 4 carbon atoms.Q^(b1) and Q^(b2) are the same as defined above.

Specific examples of the anion in the salt represented by formula (B1)include anions mentioned in JP 2010-204646 A.

Examples of the anion in the salt represented by formula (B1) arepreferably anions represented by formula (B1a-1) to formula (B1a-34).

Of these anions, the anion is preferably an anion represented by any oneof formula (B1a-1) to formula (B1a-3) and formula (B1a-7) to formula(B1a-16), formula (B1a-18), formula (B1a-19) and formula (B1a-22) toformula (B1a-34).

Examples of the organic cation of Z⁺ include an organic onium cation, anorganic sulfonium cation, an organic iodonium cation, an organicammonium cation, a benzothiazolium cation and an organic phosphoniumcation. Of these organic cations, an organic sulfonium cation and anorganic iodonium cation are preferable, and as arylsulfonium cation ismore preferable. Specific examples thereof include a cation representedby any one of formula (b2-1) to formula (b2-4) (hereinafter sometimesreferred to as “cation (b2-1)” according to the number of formula).

In formula (b2-1) to formula (b2-4).

R^(b4) to R^(b6) each independently represent a chain hydrocarbon grouphaving 1 to 30 carbon atoms, an alicyclic hydrocarbon group having 3 to36 carbon atoms or an aromatic hydrocarbon group having 6 to 36 carbonatoms, a hydrogen atom included in the chain hydrocarbon group may besubstituted with a hydroxy group, an alkoxy group having 1 to 12 carbonatoms, an alicyclic hydrocarbon group having 3 to 12 carbon atoms or anaromatic hydrocarbon group having 6 to 18 carbon atoms, a hydrogen atomincluded in the alicyclic hydrocarbon group may be substituted with ahalogen atom, an aliphatic hydrocarbon group having 1 to 18 carbonatoms, an alkylcarbonyl group having 2 to 4 carbon atoms or aglycidyloxy group, and a hydrogen atom included in the aromatichydrocarbon group may be substituted with a halogen atom, a hydroxygroup or an alkoxy group having 1 to 12 carbon atoms,

R^(b4) and R^(b5) may be bonded each other to form a ring together withsulfur atoms to which R^(b4) and R^(b3) are bonded, and —CH₂— includedin the ring may be replaced by —O—, —S— or —CO—,

R^(b7) and R^(b8) each independently represent a hydroxy group, analiphatic hydrocarbon group having 1 to 12 carbon atoms or an alkoxygroup having 1 to 12 carbon atoms,

m2 and n2 each independently represent, an integer of 0 to 5,

when m2 is 2 or more, a plurality of R^(b7) may be the same ordifferent, and when n2 is 2 or more, a plurality of R^(b8) may be thesame or different,

R^(b9) and R¹⁰ each independently represent a chain hydrocarbon grouphaving 1 to 36 carbon atoms or an alicyclic hydrocarbon group having 3to 36 carbon atoms,

R^(b9) and R^(b10) may be bonded each other to form a ring together withsulfur atoms to which R^(b5) and R^(b10) are bonded, and —CH₂— includedin the ring may be replaced by —O—, —S— or —CO—,

R^(b11) represents a hydrogen atom, a chain hydrocarbon group having 1to 36 carbon atoms, an alicyclic hydrocarbon group having 3 to 36 carbonatoms or an aromatic hydrocarbon group having 6 to 18 carbon atoms,

R^(b12) represents a chain hydrocarbon group having 1 to 12 carbonatoms, an alicyclic hydrocarbon group having 3 to 18 carbon atoms or anaromatic hydrocarbon group having 6 to 18 carbon atoms, a hydrogen atomincluded in the chain hydrocarbon may be substituted with an aromatichydrocarbon group having 6 to 18 carbon atoms, and a hydrogen atomincluded in the aromatic hydrocarbon group may be substituted with analkoxy group having 1 to 12 carbon atoms or an alkylcarbonyloxy grouphaving 1 to 12 carbon atoms,

R^(b11) and R^(b12) may be bonded each other to form a ring, including—CH—CO— to which R^(b11) and R^(b12) are bonded, and —CH₂— included inthe ring may be replaced by —O—, —S— or —CO—,

R^(b13) to R^(b18) each independently represent a hydroxy group, analiphatic hydrocarbon group having 1 to 12 carbon atoms or an alkoxygroup having 1 to 12 carbon atoms,

L^(b31) represents a sulfur atom or an oxygen atom,

o2, p2, s2 and t2 each independently represent an integer of 0 to 5,

q2 and r2 each independently represent an integer of 0 to 4,

u2 represents 0 or 1, and

when o2 is 2 or more, a plurality of R^(b13) are the same or different,when p2 is 2 or more, a plurality of R^(b14) are the same or different,when q2 is 2 or more, a plurality of R^(b15) are the same or different,when r2 is 2 or more, a plurality of R^(b16) are the same or different,when s2 is 2 or more, a plurality of R^(b17) are the same or different,and when t2 is 2 or more, a plurality of R^(b18) are the same ordifferent.

The aliphatic hydrocarbon group represents a chain hydrocarbon group andan alicyclic hydrocarbon group.

Examples of the chain hydrocarbon group include alkyl groups such as amethyl group, an ethyl group, a propyl group, an isopropyl group, abutyl group, a sec-butyl group, a tert-butyl group, a pentyl group, ahexyl group, an octyl group and a 2-ethylhexyl group.

Particularly, the chain hydrocarbon group for R^(b9) to R^(b12)preferably has 1 to 12 carbon atoms.

The alicyclic hydrocarbon group may be either monocyclic or polycyclic,and examples of the monocyclic alicyclic hydrocarbon group includecycloalkyl groups such as a cyclopropyl group, a cyclobutyl group, acyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctylgroup and a cyclodecyl group. Examples of the polycyclic alicyclichydrocarbon group include a decahydronaphthyl group, an adamantyl group,a norbornyl group and the following groups.

Particularly, the alicyclic hydrocarbon group for R^(b9) to R^(b12)preferably has 3 to 18 carbon atoms, and more preferably 4 to 12 carbonatoms.

Examples of the alicyclic hydrocarbon group in which a hydrogen atom issubstituted with an aliphatic hydrocarbon group include amethylcyclohexyl group, a dimethylcyclohexyl group, a2-methyladamantan-2-yl group, a 2-ethyladamantan-2-yl group, a2-isopropyladamantan-2-yl group, a methylnorbornyl group, an isobornylgroup and the like. In the alicyclic hydrocarbon group in which ahydrogen atom is substituted with an aliphatic hydrocarbon group, thetotal number of carbon atoms of the alicyclic hydrocarbon group and. thealiphatic hydrocarbon group is preferably 20 or less.

Examples of the aromatic hydrocarbon group include aryl groups such as aphenyl group, a biphenyl group, a naphthyl group and a phenanthrylgroup. The aromatic hydrocarbon group may have a chain hydrocarbon groupor an alicyclic hydrocarbon group, and examples thereof include anaromatic hydrocarbon group having a chain hydrocarbon group having 1 to18 carbon atoms (a tolyl group, a xylyl group, a cumenyl group, amesityl group, a p-ethylphenyl group, a p-tert-butylphenyl group, a2,6-diethylphenyl group, a 2-methyl-6-ethylphenyl group, etc.) and anaromatic hydrocarbon group having an alicyclic hydrocarbon group having3 to 18 carbon atoms (a p-cyclohexylphenyl group, a p-adamantylphenylgroup, etc.). When the aromatic hydrocarbon group has a chainhydrocarbon group or an alicyclic hydrocarbon group, a chain hydrocarbongroup having 1 to 18 carbon atoms and an alicyclic hydrocarbon grouphaving 3 to 18 carbon atoms are preferable.

Examples of the aromatic hydrocarbon group in which a hydrogen atom issubstituted with an alkoxy group include a p-methoxyphenyl group and thelike.

Examples of the chain hydrocarbon group in which a hydrogen atom issubstituted with an aromatic hydrocarbon group include aralkyl groupssuch as a benzyl group, a phenethyl group, a phenylpropyl group, atrityl group, a naphthylmethyl group and a naphthylethyl group.

Examples of the alkoxy group include a methoxy group, an ethoxy group, apropoxy group, a butoxy group, a pentyloxy group, a hexyloxy group, aheptyloxy group, an octyloxy group, a decyloxy group and a dodecyloxygroup.

Examples of the alkylcarbonyl group include an acetyl group, a propionylgroup and a butyryl group.

Examples of the halogen atom include a fluorine atom, a chlorine atom, abromine atom and an iodine atom.

Examples of the alkylcarbonyloxy group include a methylcarbonyloxygroup, an ethylcarbonyloxy group, a propylcarbonyloxy group, anisopropylcarbonyloxy group, a butylcarbonyloxy group, asec-butylcarbonyloxy group, a tert-butylcarbonyloxy group, apentylcarbonyloxy group, a hexylcarbonyloxy group, an octylcarbonyloxygroup and a 2-ethylhexylcarbonyloxy group.

The ring formed by bonding R^(b4) and R^(b5) each other, together withsulfur atoms to which R^(b4) and R^(b3) are bonded, may be a monocyclic,polycyclic, aromatic, nonaromatic, saturated or unsaturated ring. Thisring includes a ring having 3 to 18 carbon atoms and is preferably aring having 4 to 18 carbon atoms. The ring containing a sulfur atomincludes a 3-membered to 12-membered ring and is preferably a 3-memberedto 7-membered ring and includes, for example, the following rings. *represents a bonding site.

The ring formed by bonding R^(b9) and R^(b10) each other may be amonocyclic, polycyclic, aromatic, nonaromatic, saturated or unsaturatedring. This ring includes a 3-membered to 12-membered ring and ispreferably a 3-membered to 7-membered ring. The ring includes, forexample, a thiolan-1-ium ring (tetrahydrothiophenium ring), athian-1-ium ring, a 1,4-oxathian-4-ium ring and the like.

The ring formed by bonding R^(b11) and R^(b12) each other may be amonocyclic, polycyclic, aromatic, nonaromatic, saturated or unsaturatedring. This ring includes a 3-membered to 12-membered ring and ispreferably a 3-membered to 7-membered ring. Examples thereof include anoxocycloheptane ring, as oxocyclohexane ring, an oxonorbornane ring, anoxoadamantane ring and the like.

Of cation (b2-1) to cation (b2-4), a cation (b2-1) is preferable.

Examples of the cation (b2-1) include the following cations.

Examples of the cation (b2-2) include the following cations.

Examples of the cation (b2-3) include the following cations.

Examples of the cation (b2-4) include the following cations.

The acid generator (B) is a combination of the above-mentioned anionsand the above-mentioned organic cations, and these can be optionallycombined. Examples of the acid generator (B) are preferably combinationsof anions represented by any one of formula (B1a-1) to formula (B1a-3)and formula (B1a-7) to formula (B1a-16), formula (B1a-18), formula(B1a-19) and formula (B1a-22) to formula (B1a-34) with a cation (b2-1)or a cation (b2-3).

Examples of the acid generator (B) are preferably those represented byformula (B1-1) to formula (B1-48) of these, those containing anarylsulfonium cation are preferable, and those represented by formula(B1-1) to formula (B1-3), formula (B1-5) to formula (B1-7), formula(B1-11) to formula (B1-14), formula (B1-20) to formula (B1-26), formula(B1-29) and formula (B1-31) to formula (B1-48) are particularlypreferable.

In the resist composition of the present invention, the content of theacid generator is preferably 1 part by mass or more and 40 parts by massor less, and more preferably 3 parts by mass or more and 40 parts bymass or less based on 100 parts by mass of the resin (A).

<Solvent (E)>

The content of the solvent (E) in the resist composition is usually 90%by mass or more and 99.9% by mass or less, preferably 92% by mass ormore and 99% by mass or less, and more preferably 94% by mass or moreand 99% by mass or less. The content of the solvent (E) can be measured,for example, by a known analysis means such as liquid chromatography orgas chromatography.

Examples of the solvent (E) include glycol ether esters such asethylcellosolve acetate, methylcellosolve acetate and propylene glycolmonomethyl ether acetate; glycol ethers such as propylene glycolmonomethyl ether; esters such as ethyl lactate, butyl acetate, amylacetate and ethyl pyruvate; ketones such as acetone, methyl isobutylketone, 2-heptanone and cyclohexanone; and cyclic esters such asγ-butyrolactone. The solvent (E) may be used alone, or two or moresolvents may be used.

<Quencher (C)>

Examples of the quencher (C) include a basic nitrogen-containing organiccompound and a salt generating an acid having an acidity lower than thatof an acid generated from an acid generator (B). The content of thequencher (C) is preferably about 0.01 to 5% by mass, and more preferablyabout 0.01 to 3% by mass based on the amount of the solid component ofthe resist composition.

Examples of the basic nitrogen-containing organic compound include amineand an ammonium salt. Examples of the amine include an aliphatic amineand an aromatic amine. Examples of the aliphatic amine include a primaryamine, a secondary amine and a tertiary amine.

Examples of the amine include 1-naphthylamine, 2-naphthylamine, aniline,diisopropylaniline, 2-,3- or 4-methylaniline, 4-nitroaniline,N-methylaniline, N,N-dimethylaniline, diphenylamine, hexylamine,heptylamine, octylamine, nonylamine, decylamine, dibutylamine,dipentylamine, dihexylamine, diheptylamine, dioctylamine, dinonylamine,didecylamine, triethylamine, trimethylamine, tripropylamine,tributylamine, tripentylamine, trihexylamine, triheptylamine,trioctylamine, trthonylamine, tridecylamine, methyldibutylamine,methyldipentylamine, methyldihexylamine, methyldicyclohexylamine,methyldtheptylamine, methyldioctylamine, methyldinonylamine,methyldidecylamine, ethyldibutylamine, ethyldipentylamine,ethyldihexylamine, ethyldiheptylamine, ethyldioctylamine,ethyldinonylamine, ethyldidecylamine, dicyclohexylmethylamine,tris[2-(2-methoxyethoxy)ethyl]amine, triisopropanolamine,ethylenediamine, tetramethylenediamine, hexamethylenediamine,4,4′-diamino-1,2-diphenylethane,4,4′-diamino-3,3′-dimethyldiphenylmethane,4,4′-diamino-3,3′-diethyldiphenylmethane, 2,2′-methylenebisaniline,imidazole, 4-methylimidazole, pyridine, 4-methylpyridine,1,2-di(2-pyridyl)ethane, 1,2-di(4-pyridyl)ethane,1,2-di(2-pyridyl)ethene, 1,2-di(4-pyridyl)ethene,1,3-di(4-pyridyl)propane, 1,2-di(4-pyridyloxy)ethane,di(2-pyridyl)ketone, 4,4′-dipyridylsulfide, 4,4′-dipyridyldisulfide,2,2′-dipyridylamine, 2,2′-dipcolylamine, bipyridine and the like,preferably diisopropylaniline, and more preferably2,6-diisopropylaniline.

Examples of the ammonium salt include tetramethylammonium hydroxide,tetraisopropylammonium hydroxide, tetrabutylammonium hydroxide,tetrahexylammonium hydroxide, tetraoctylammonium hydroxide,phenyltrimethylammonium hydroxide,3-(trifluoromethyl)phenyltrimethylammonium hydroxide,tetra-n-butylammonium salicylate and choline.

The acidity in a salt generating an acid having an acidity lower thanthat of an acid generated from the acid generator (B) is indicated bythe acid dissociation constant (pKa). Regarding the salt generating anacid having an acidity lower than that of an acid generated from theacid generator (B), the acid dissociation constant of an acid generatedfrom the salt usually meets the following inequality: −3<pKa, preferably−1<pKa<7, and more Preferably 0<pKa<5.

Examples of the salt generating an acid having an acidity lower thanthat of an acid generated from the acid generator (B) include saltsrepresented by the following formulas, a salt represented by formula (D)mentioned in JP 2015-147926 A (hereinafter sometimes referred to as“weak acid inner salt (D)”, and salts mentioned in JP 2012-229206 A, JP2012-6908 A, JP 2012-72109 A, JP 2011-39502 A and JP 2011-191745 A. Aweak acid inner salt (D) is preferable.

Examples of the weak acid inner salt (D) include the following salts.

<Other Components>

If necessary, the resist composition of the present invention may alsoinclude components other than the components mentioned above(hereinafter sometimes referred to as “other components (F)”). The othercomponents (F) are not particularly limited and it is possible to usevarious additives known in the resist field, for example, sensitizers,dissolution inhibitors, surfactants, stabilizers, dyes and the like.

<Preparation of Resist Composition>

The resist composition of the present invention can be prepared bymixing a resin (A) and an acid generator (B) of the present invention,and if necessary, resins other than the resin (A) (a resin (AY), a resin(AZ), a resin (X), etc.), a quencher (C) such as a salt generating anacid having an acidity lower than that of an acid generated from an acidgenerator, a solvent (E) and other components (F). The order of mixingthese components is any order and is not particularly limited. It ispossible to select, as the temperature during mixing, appropriatetemperature from 10 to 40° C., according to the type of the resin, thesolubility in the solvent (E) of the resin and the like. It is possibleto select, as the mixing time, appropriate time from 0.5 to 24 hoursaccording to the mixing temperature. The mixing means is notparticularly limited and it is possible to use mixing with stirring.

After mixing the respective components, the mixture is preferablyfiltered through a filter having a pore diameter of about 0.003 to 0.2μm.

<Method for Producing Resist Pattern>

The method for producing a resist pattern of the present inventioncomprises:

-   (1) a step of applying the resist composition of the present    invention on a substrate,-   (2) a step of drying the applied composition to form a composition    layer,-   (3) a step of exposing the composition layer,-   (4) a step of heating the exposed composition layer, and-   (5) a step of developing the heated composition layer.

The resist composition can be usually applied on a substrate using aconventionally used apparatus, such as a spin coater. Examples of thesubstrate include inorganic substrates such as a silicon wafer. Beforeapplying the resist composition, the substrate may be washed, and anorganic antireflection film may be formed on the substrate.

The solvent is removed by drying the applied. composition to form acomposition layer. Drying is performed by evaporating the solvent usinga heating device such as a hot plate (so-called. “prebake”), or adecompression device. The heating temperature is preferably 50 to 200°C. and the heating time is preferably 10 to 180 seconds. The pressureduring drying under reduced pressure is preferably about 1 to 1.0×10⁵Pa.

The composition layer thus obtained is usually exposed using an aligner.The aligner may be a liquid immersion. aligner. It is possible to use,as an exposure source, various exposure sources, for example, exposuresources capable of emitting laser beam in an ultraviolet region such asKrF excimer laser (wavelength of 248 nm), ArF excimer laser (wavelengthof 193 nm) and F₂ excimer laser (wavelength of 157 nm), an exposuresource capable of emitting harmonic laser beam in a far-ultraviolet orvacuum ultra violet region by wavelength-converting laser beam from asolid-state laser source (YAG or semiconductor laser), an exposuresource capable of emitting electron beam or extreme ultraviolet (ELMlight and the like. As used herein, such exposure to radiation issometimes collectively referred to as “exposure”. The exposure isusually performed through a mask corresponding to a pattern to berequired. When electron beam is used as the exposure source, exposuremay be performed by direct writing without using the mask.

The exposed composition layer is subjected to a heat. treatment(so-called “post-exposure bake”) to promote the deprotection reaction inan acid-labile group. The heating temperature is usually about 50 to200° C., and preferably about 70 to 150° C.

The heated composition layer is usually developed with a developingsolution using a development apparatus. Examples of the developingmethod include a dipping method, a paddle method, a spraying method, adynamic dispensing method and the like. The developing temperature ispreferably, for example, 5 to 60° C. and the developing time ispreferably, for example, 5 to 300 seconds. It is possible to produce apositive resist pattern or negative resist pattern by selecting the typeof the developing solution as follows.

When the positive resist pattern is produced from the resist compositionof the present invention, an alkaline developing solution is used as thedeveloping solution. The alkaline developing solution may be variousaqueous alkaline solutions used in this field. Examples thereof includeaqueous solutions of tetramethylammonium hydroxide and(2-hydroxyethyl)trimethylammonium hydroxide (commonly known a.scholine). The surfactant may he contained in the alkaline developingsolution.

It is preferable that the developed resist pattern is washed withultrapure water and then water remaining on the substrate and thepattern is removed.

When the negative resist pattern is produced from the resist compositionof the present invention, a developing solution containing an organicsolvent (hereinafter sometimes referred to as “organic developingsolution”) is used as the developing solution.

Examples of the organic solvent contained in the organic developingsolution include ketone solvents such as 2-hexanone and 2-heptanone;glycol ether ester solvents such as propylene glycol monomethyl etheracetate; ester solvents such as butyl acetate; glycol ether solventssuch as propylene glycol monomethyl ether; amide solvents such asN,N-dimethylacetamide; and aromatic hydrocarbon solvents such asanisole.

The content of the organic solvent in the organic developing solution ispreferably 90% by mass or more and 100% by mass or less, more preferably95% by mass or more and 100% by mass or less, and still more preferablythe organic developing solution is substantially composed only of theorganic solvent.

Particularly, the organic developing solution is preferably a developingsolution containing butyl acetate and/or 2-heptanone. The total contentof butyl acetate and 2-heptanone in the organic developing solution ispreferably 50% by mass or more and 100% by mass or less, more preferably90% by mass or more and 100% by mass or less, and more preferably theorganic developing solution is substantially composed only of butylacetate and/or 2-heptanone.

The surfactant may be contained in the organic developing solution. Atrace amount of water may be contained in the organic developingsolution.

During development, the development may be stopped by replacing by asolvent with the type different from that of the organic developingsolution.

The developed resist pattern is preferably washed with a rinsingsolution. The rinsing solution is not particularly limited as long as itdoes not dissolve the resist pattern, and it is possible to use asolution containing an ordinary organic solvent which is preferably analcohol solvent or an ester solvent.

After washing, the rinsing solution remaining on the substrate and thepattern is preferably removed.

<Applications>

The resist composition of the present invention is suitable as a resistcomposition for exposure of KrF excimer laser, a resist composition forexposure of ArF excimer laser, a resist composition for exposure ofelectron beam (EB) or a resist composition for exposure of EUV, and moresuitable as a resist composition for exposure of electron beam (EB) or aresist composition for exposure of EUV, and. the resist composition isuseful for fine processing of semiconductors.

EXAMPLES

The present invention will be described more specifically by way ofExamples. Percentages and parts expressing the contents or amounts usedin the Examples are by mass unless otherwise specified.

The weight-average molecular weight is a value determined by gelpermeation chromatography under the following conditions.

Equipment: HIPC-8120 GPC type (manufactured by TOSOH CORPORATION)

Column: TSKgel Multipore H_(XL)-M×3+guardcolumn (manufactured by TOSOHCORPORATION)

Eluent: tetrahydrofuran

Flow rate: 1.0 mL/min

Detector: RI detector

Column temperature: 4.0° C.

Injection amount: 100 μl

Molecular weight standards: polystyrene standard (manufactured by TOSOHCORPORATION)

Structures of compounds were confirmed by measuring a molecular ion peakusing mass spectrometry (Liquid Chromatography: Model 1100, manufacturedby Agilent. Technologies, Inc., Mass Spectrometry: Model LC/MSD,manufactured by Agilent Technologies, Inc.). In the following Examples,the value of this molecular ion peak is indicated by “MASS”.

Synthesis of Resin

Compounds (monomers) used in the synthesis of resins are shown below.

Hereinafter, these monomers are referred to as “monomer (a1-1-3)”according to the number of formula.

Example 1 [Synthesis of Resin A1]

Using a monomer (a1-4-2), a monomer (a1-1-3), a monomer (a1-5-1) and amonomer (I-1) as monomers, these monomers were mixed in a molar ratio of32:26:30:12 [monomer (a1-4-2):monomer (a1-1-3):monomer (a1-5-1):monomer(I-1)]. This monomer mixture was mixed with methyl isobutyl ketone inthe amount of 1.5 mass times the total mass of all monomers. To themixture thus obtained, azobisisobutyronitrile andazobis(2,4-dimethylvaleronitrile) as initiators were added in theamounts of 2.1 mol % and 6.3 mol % based on the total molar number ofall monomers, and then polymerization was performed by heating at 73° C.for about 5 hours. Thereafter, an aqueous p-toluenesulfonic acidsolution was added, followed by stirring for 6 hours and furtherisolation through separation. The organic layer thus recovered waspoured into a large amount of n-heptane to precipitate a resin, followedby filtration and recovery to obtain a resin A1 (copolymer) having aweight-average molecular weight of about 5.7×10³ in a yield of 62%. Thisresin A1 includes the following structural units.

Example 2 [Synthesis of Resin A2]

Using acetoxystyrene, a monomer (a1-1-3), a monomer (a1-5-1) and amonomer (I-1) as monomers, these monomers were mixed in a molar ratio of32:26:30:12 [acetoxystyrene:monomer (a1-1-3):monomer (a1-5-1) :monomer(I-1)]. This monomer mixture was mixed with methyl isobutyl ketone inthe amount of 1.5 mass times the total mass of all monomers. To themixture thus obtained, azobisisobutyronitrile andazobis(2,4-dimethylvaleronitrile) as initiators were added in theamounts of 2.1 mol % and 6.3 mol % based on the total molar number ofall monomers, and then polymerization was performed by heating at 73° C.for about 5 hours. Thereafter, an aqueous 25% tetramethylammoniumhydroxide solution was added to the polymerization reaction solution,followed by stirring for 12 hours and further isolation throughseparation. The organic layer thus obtained was poured into a largeamount of n-heptane to precipitate a resin, followed by filtration andrecovery to obtain a resin A2 (copolymer) having a weight-averagemolecular weight of about 5.9×10³ in a yield of 73%. This resin A2includes the following structural units.

Example 3 [Synthesis of Resin A3]

Using a monomer (a1-4-2), a monomer (a3-2-1), a monomer (a1-5-1) and amonomer (I-1) as monomers, these monomers were mixed in a molar ratio of30:10:50:10 [monomer (a1-4-2):monomer (a3-2-1):monomer (a1-5-1):monomer(I-1)]. This monomer mixture was mixed with methyl isobutyl ketone inthe amount of 1.5 mass times the total mass of all monomers. To themixture thus obtained, azobisisobutyronitrile andazobis(2,4-dimethylvaleronitrile) as initiators were added in theamounts of 2.1 mol % and 6.3 mol % based on the total molar number ofail monomers, followed by heating at 73° C. for about 5 hours.Thereafter, the polymerization reaction solution was cooled to 23° C.and an aqueous p-toluenesulfonic acid solution was added, followed bystirring for 3 hours and further isolation through separation. Theorganic layer thus recovered was poured into a large amount of n-heptaneto precipitate a resin, followed by filtration and recovery to obtain aresin A3 (copolymer) having a weight-average molecular weight of about5.5×10³ in a yield of 58%. This resin A3 includes the followingstructural units.

Example 4 [Synthesis of Resin A4]

Using a monomer (a1-4-2), a monomer (a1-1-3), a monomer (a3-2-1), amonomer (a1-5-1) and a monomer (I-1) as monomers, these monomers weremixed in a molar ratio of 30:20:10:30:10 [monomer (a1-4-2):monomer(a1-1-3):monomer (a3-2-1):monomer (a1-5-1) :monomer (I-1)]. This monomermixture was mixed with methyl isobutyl ketone in the amount of 1.5 masstimes the total mass of all monomers. To the mixture thus obtained,azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) asinitiators were added in the amounts of 2.1 mol % and 6.3 mol % based onthe total molar number of all monomers, followed by heating at 73° C.for about 5 hours. Thereafter, the polymerization reaction solution wascooled to 23° C. and an aqueous p-toluenesulfonic acid solution wasadded, followed by starring for 3 hours and further isolation throughseparation. The organic layer thus recovered was poured into a largeamount of n-heptane to precipitate a resin, followed by filtration andrecovery to obtain a resin A4 (copolymer) having a weight-averagemolecular weight of about 5.7×10³ in a yield of 60%. This resin A4includes the following structural units.

Example 5 [Synthesis of Resin A5]

Using a monomer (a1-4-2), a monomer (a1-1-3), a monomer (a2-1-3), amonomer (a3-2-1), a monomer (a1-5-1) and a monomer (1-1) as monomers,these monomers were mixed in a molar ratio of 30:20:3:7:30:10 [monomer(a1-4-2):monomer (a1-1-3) ;monomer (a2-1-3) :monomer (a3-2-1) :monomer(a1-5-1):monomer (I-1)]. This monomer mixture was mixed with methylisobutyl ketone in the amount of 1.5 mass times the total mass of allmonomers. To the mixture thus obtained, azobisisobutyronitrile andazobis(2,4-dimethylvaleronitrile) as initiators were added in theamounts of 2.1 mol % and 6.3 mol % based on the total molar number ofall monomers, followed by heating at 73° C. for about 5 hours.Thereafter, the polymerization reaction solution was cooled to 23° C.and an aqueous p-toluenesulfonic acid solution was added, followed bystirring for 3 hours and further isolation through separation. Theorganic layer thus recovered was poured into a large amount of n-heptaneto precipitate a resin, followed by filtration and recovery to obtain aresin A5 (copolymer) having a weight-average molecular weight of about5.8×10³ in a yield of 60%. This resin A5 includes the followingstructural units.

Example 6 [Synthesis of Resin A6]

Using a monomer (a1-5-1) and a monomer (I-1) as monomers, these monomerswere mixed in a molar ratio of 38:62 [monomer (a1-5-1):monomer (I-1)].This monomer mixture was mixed with methyl isobutyl ketone in the amountof 1.5 mass times the total mass of all monomers. To the mixture thusobtained, azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile)as initiators were added in the amounts of 2.1 mol % and 6.3 mol % usedon the total molar number of all monomers, and then polymerization wasperformed by heating at 73° C. for about 5 hours. Thereafter, thepolymerization reaction solution was cooled to 23° C. and then pouredinto a large amount of n-heptane to precipitate a resin, followed byfiltration and recovery to obtain a resin A6 (copolymer) having aweight-average molecular weight of about 5.9×10³ in a yield of 67%. Thisresin A6 includes the following structural units.

Example 7 [Synthesis of Resin A7]

Using a monomer (a1-5-1) and a monomer (I-1) as monomers, these monomerswere mixed in a molar ratio of 70:30 [monomer (a1-5-1) :monomer (I-1)].This monomer mixture was mixed with methyl isobutyl ketone in the amountof 1.5 mass times the total mass of all monomers. To the mixture thusobtained, azobisisobutyrontrile and azobis(2,4-dimethylvaieronitrile) asinitiators were added in the amounts of 2.1 mol % and 6.3 mol % based onthe total molar number of all monomers, and then polymerization wasperformed by heating at 73° C. for about 5 hours. Thereafter, thepolymerization reaction solution was cooled to 23° C. and then pouredinto a large amount of n-heptane to precipitate a resin, followed byfiltration and recovery to obtain a resin A7 (copolymer) having aweight-average molecular weight of about 5.5×10³ in a yield of 55%. Thisresin A7 includes the following structural units.

Example 8 [Synthesis of Resin A8]

Using a monomer (a3-2-1), a monomer (a1-5-1) and a monomer (I-1) asmonomers, these monomers were mixed in a molar ratio of 10:50:40[monomer (a3-2-1):monomer (a1-5-1) monomer (I-1)]. This monomer mixturewas mixed with methyl isobutyl ketone in the amount of 1.5 mass timesthe total mass of all monomers. To the mixture thus obtained,azobisisobutyronitrile and azobis (2, 4 -dimethylvraleronitrile) asinitiators were added in the amounts of 2.1 mol % and 6.3 mol % based onthe total molar number of all monomers, followed by heating at 73° C.for about 5 hours. Thereafter, the polymerization reaction solution wascooled to 23° C. and then was poured into a large amount of n-heptane toprecipitate a resin, followed by filtration and recovery to obtain aresin AB (copolymer) having: a weight-average molecular weight of about5.9×10³ in a yield of 58%. This resin A8 includes the followingstructural units.

Example 9 [Synthesis of Resin A9]

Using acetoxystyrene, a monomer (a1-1-3), a monomer (a1-5-5) and amonomer (I-1) as monomers, these monomers were mixed in a molar ratio of32:26:30:12 [acetoxystyrene:monomer (a1-1-3) :monomer (a1-5-5) :monomer(I-1)]. This monomer mixture was mixed with methyl isobutyl ketone inthe amount of 1.5 mass times the total mass of all monomers. To themixture thus obtained, azobisisobutyronitrile andazobis(2,4-dimethylvaleronitrile) as initiators were added in theamounts of 2.1 mol % and 6.3 mol % based on the total molar number ofall monomers, and then polymerization was performed by heating at 73° C.for about 5 hours. Thereafter, an aqueous 25% tetramethylammoniumhydroxide solution was added to the polymerization reaction solution,followed by stirring for 12 hours and further isolation throughseparation. The organic layer thus obtained was poured into a largeamount of n-heptane to precipitate a resin, followed by filtration andrecovery to obtain a resin A9 (copolymer) having a weight averagemolecular weight of about 6.1×10³ in a yield of 68%. This resin A9includes the following structural units.

Example 10 [Synthesis of Resin A10]

Using acetoxystyrene, a monomer (a1-1-3), a monomer (a1-5-3) and amonomer (I-1) as monomers, these monomers were mixed in a molar ratio of32:26:30:12 [acetoxystyrene:monomer (a1-1-3) :monomer (a1-5-3):monomer(I-1)]. This monomer mixture was mixed with methyl isobutyl ketone inthe amount of 1.5 mass times the total mass of all monomers. To themixture thus obtained, azobisisobutyronitrile andazobis(2,4-dimethylvaleronitrile) as initiators were added in theamounts of 2.1 mol % and 6.3 mol % based on the total molar number ofall monomers, and then polymerization was performed by heating at 73° C.for about 5 hours. Thereafter, an aqueous 25% tetramethylammoniumhydroxide solution was added to the polymerization reaction solution,followed by stirring for 12 hours and further isolation throughseparation. The organic layer thus recovered was poured into a largeamount of n-heptane to precipitate a resin, followed by filtration andrecovery to obtain a resin A10 (copolymer) having a weight-averagemolecular weight of about 5.6×10³ in a yield of 61%. This resin A10includes the following structural units.

Example 11 [Synthesis of Resin A11]

Using a monomer (a1-4-2), a monomer (a1-1-3), a monomer (a2-1-3), amonomer (a3-2-1), a monomer (a1-5-5) and a monomer (I-1) as monomers,these monomers were mixed in a molar ratio of 30:20:3:7:30:10 [monomer(a1-4-2):monomer (a1-1-3):monomer (a2-1-3):monomer (a3-2-1):monomer(a1-5-5):monomer (I-1)]. This monomer mixture was mixed with methylisobutyl ketone in the amount of 1.5 mass times the total mass of allmonomers. To the mixture thus obtained, azobisisobutyronitrile andazobis(2,4-dimethylvaleronitrile) as initiators were added in theamounts of 2.1 mol % and 6.3 mol % based on the total molar number ofall monomers, followed by heating at 73° C. for about 5 hours.Thereafter, the polymerization reaction solution was cooled to 23° C.and an aqueous p-toluenesulfonic acid solution was added, followed bystirring for 3 hours and further isolation through separation. Theorganic layer thus recovered was poured into a large amount of n-heptaneto precipitate a resin., followed by filtration and recovery to obtain aresin. All (copolymer) having a weight-average molecular weight of about6.1×10³ in a yield of 58%. This resin A11 includes the followingstructural units.

Example 12 [Synthesis of Resin A12]

Using a monomer (a1-4-2), a monomer (a1-1-3), a monomer (a2-1-3), amonomer (a3-2-1), a monomer (a1-5-3) and a monomer (I-1) as monomers,these monomers were mixed in a molar ratio of 30:20:3:7:30:10 [monomer(a1-4-2) :monomer (a1-1-3) ;monomer (a2-1-3) :monomer (a3-2-1) :monomer(a1-5-3):monomer (I-1)]. This monomer mixture was mixed with methylisobutyl ketone in the amount of 1.5 mass times the total mass of allmonomers. To the mixture thus obtained, azobisisobutyronitrile andazobis(2,4-dimethylvaleronitrile) as initiators were added in theamounts of 2.1 mol % and 6.3 mol % based on the total molar number ofall monomers, followed by heating at 73° C. for about 5 hours.Thereafter, the polymerization reaction solution was cooled to 23° C.and an aqueous p-toluenesulfonic acid solution was added, followed bystirring for 3 hours and further isolation through separation. Theorganic layer thus recovered was poured into a large amount of n-heptaneto precipitate a resin., followed by filtration and recovery to obtain aresin. A12 (copolymer) having a weight-average molecular weight of about5.6×10³ in a yield of 53%. This resin A12 includes the followingstructural units.

Synthesis Example 1 [Synthesis of Resin AX1]

Using acetoxystyrene and a monomer (a1-5-X1) as monomers, these monomerswere mixed in a molar ratio of 70:30 [acetoxystyrene:monomer (a1-5-X1)].This monomer mixture was mixed with methyl isobutyl ketone in the amountof 1.5 mass times the total mass of all monomers. To the mixture thusobtained, azobisisobutvronitrile and azobis(2,4-dimethylvaleronitrile)as initiators were added in the amounts of 2.1 mol % and 6.3 mol % basedon the total molar number of ail monomers, and then polymerization wasperformed by heating at 73° C. for about 5 hours. Thereafter, an aqueous25% tetramethviammonium hydroxide solution was added to thepolymerization reaction solution, followed by stirring for 12 hours andfurther isolation through separation. The organic layer thus obtainedwas poured into a large amount of n-heptane to precipitate a resin,followed by filtration and recovery to obtain a resin AX1 (copolymer)having a weight-average molecular weight of about 5.8×10³ in a yield of75%. This resin AX1 includes the following structural units.

Synthesis Example 2 [Synthesis of Resin AX2]

Using a monomer (a1-4-2), a monomer (a3-2-1) and a monomer (a1-5-X2) asmonomers, these monomers were mixed in a molar ratio of 30:10:60[monomer (a1-4-2) :monomer (a3-2-1): monomer (a1-5-2)]. This monomermixture was mixed with methyl isobutyl ketone in the amount of 1.5 masstimes the total mass of all monomers. To the mixture thus obtained,azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) asinitiators were added in the amounts of 2.1 mol % and 6.3 mol % based onthe total molar number of all monomers, followed by heating at 73° C.for about 5 hours. Thereafter, the polymerization reaction solution wascooled to 23° C. and. an aqueous p-toluenesulfonic acid solution wasadded, followed by stirring for 3 hours and further isolation throughseparation. The organic layer thus recovered was poured into a largeamount of n-heptane to precipitate a resin, followed by filtration andrecovery to obtain a resin AX2 (copolymer) having a weight-averagemolecular weight of about 5.7×10³ in a yield of 60%. This resin AX2includes the following structural units.

Synthesis Example 3 [Synthesis of Resin AX3]

Using a monomer (a1-1-1) and a monomer (I-1) as monomers, these monomerswere mixed in a molar ratio of 31:69 [monomer (a1-1-1):monomer (I-1)].This monomer mixture was mixed with methyl isobutyl ketone in the amountof 1.5 mass times the total mass of all monomers. To the mixture thusobtained, azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile)as initiators were added in the amounts of 2.1 mol % and 6.3 mol % basedon the total molar number of all monomers, and then polymerization wasperformed by heating at 73° C. for about 5 hours. Thereafter, thepolymerization reaction solution was poured into a large amount ofn-heptane to precipitate a resin, followed by filtration and recovery toobtain a resin AX3 (copolymer) having a weight-average molecular weightof about 5.8×10³ in a yield of 80%. This resin AX3 includes thefollowing structural units.

Synthesis Example 4 [Synthesis of Resin AX4]

Using a monomer (a1-4-2), a monomer (a1-1-2), a monomer (II-2-A1) and amonomer (I-1) as monomers, these monomers were mixed in a molar ratio of30:35:5:30 [monomer (a1-4-2):monomer (a1-1-2):monomer (II-2-A1) :monomer(I-1)]. This monomer mixture was mixed with methyl isobutyl ketone inthe amount of 1.5 mass times the total mass of all monomers. To themixture thus obtained, azobisisobutyronitrile andazobis(2,4-dimethylvaleronitrile) as initiators were added in theamounts of 2.1 mol % and 6.3 mol % based on the total molar number ofall monomers, and then polymerization was performed by heating at 13° C.for about 5 hours. Thereafter, an aqueous p-toluenesulfonic acidsolution was added, followed by stirring for 6 hours and furtherisolation through separation. The organic layer thus recovered waspoured into a large amount of n-heptane to precipitate a resin, followedby filtration and recovery to obtain a resin. AX4 (copolymer) having aweight-average molecular weight of about 5.6×10³ in a yield of 61%. Thisresin AX4 includes the following structural units.

<Preparation of Resist Composition>

A mixture obtained by mixing and dissolving the respective componentsshown in Table 1 was filtered through a fluororesin filter having a porediameter of 0.2 μm to prepare resist compositions.

TABLE 1 Resist Acid composition Resin generator Quencher PB/PEBComposition 1 A1 = B1-43 = D1 = 130° C./120° C. 10 parts 3.4 parts 0.7parts Composition 2 A2 = B1-43 = D1 = 130° C./120° C. 10 parts 3.4 parts0.7 parts Composition 3 A3 = B1-43 = D1 = 130° C./120° C. 10 parts 3.4parts 0.7 parts Composition 4 A4 = B1-43 = D1 = 130° C./120° C. 10 parts3.4 parts 0.7 parts Composition 5 A5 = B1-43 = D1 = 130° C./120° C. 10parts 3.4 parts 0.7 parts Composition 6 A6 = B1-43 = D1 = 130° C./120°C. 10 parts 3.4 parts 0.7 parts Composition 7 A7 = B1-43 = D1 = 130°C./120° C. 10 parts 3.4 parts 0.7 parts Composition 8 A8 = B1-43 = D1 =130° C./120° C. 10 parts 3.4 parts 0.7 parts Composition a A9 = B1-43 =D1 = 130° C./120° C. 10 parts 3.4 parts 0.7 parts Composition 10 A10 =B1-43 = D1 = 130° C./120° C. 10 parts 3.4 parts 0.7 parts Composition 11A11 = B1-43 = D1 = 130° C./120° C. 10 parts 3.4 parts 0.7 partsComposition 12 A12 = B1-43 = D1 = 130° C./120° C. 10 parts 3.4 parts 0.7parts Comparative AX1 = B1-43 = D1 = 130° C./120° C. Composition 1 10parts 3.4 parts 0.7 parts Comparative AX2 = B1-43 = D1 = 130° C./120° C.Composition 2 10 parts 3.4 parts 0.7 parts Comparative AX3 = B1-43 = D1= 130° C./120° C. Composition 3 10 parts 3.4 parts 0.7 parts ComparativeAX4 = B1-43 = D1 = 130° C./120° C. Composition 4 10 parts 3.4 parts 0.7parts

<Resin>

A1 to A12, AX1 to AX4: Resin A1 to Resin A12, Resin AX1 to Resin AX4

<Acid Generator (B)>

B1-43: Salt represented by formula (B1-43) (synthesized in accordancewith Examples of JP 2016-47815 A)

<Quencher (C): Salt Generating an Acid Having an Acidity Lower than thatof an Acid Generated from an Acid Generator>

D1: synthesized by the method mentioned in JP 2011-39502 A

<Solvent>

Propylene glycol monomethyl ether acetate 400 parts Propylene glycolmonomethyl ether 150 parts γ-Butyrolactone  5 parts(Evaluation of Exposure of Resist Composition with Electron Beam:Alkaline Development)

Each. 6 inch-diameter silicon wafer was treated withhexamethyldisilazane on a direct hot plate at 90° C. for 60 seconds. Aresist composition was spin-coated on the silicon wafer in such a mannerthat the thickness of the composition layer became 0.04 μm. The coatedsilicon wafer was prebaked on the direct hot plate at the temperatureshown in the column “PB” of Table 1 for 60 seconds to form a compositionlayer. Using an electron-beam direct-write system (“ELS-F125 125 keV”,manufactured by ELIONIX INC.), contact hole patterns (hole pitch of 40nm/hole diameter of 17 nm) were directly written on the compositionlayer formed on the wafer while changing the exposure dose stepwise.

After the exposure, post-exposure baking was performed on the hot plateat the temperature shown in the column “PEB” of Table 1 for 60 seconds,followed by paddle development, with an aqueous 2.38% by masstetramethylammonium hydroxide solution for 60 seconds to obtain a resistpattern.

In the resist pattern thus obtained after the exposure, effectivesensitivity was defined as the exposure dose at which a hole diameter of17 nm of the pattern formed.

<Evaluation of CD Uniformity (CDU)>

In the effective sensitivity, the hole diameter of the pattern formedwith a hole dimeter of 17 nm was determined by measuring 24 times perone hole and the average of the measured values was regarded as theaverage hole diameter. The standard deviation determined under theconditions that the average diameter of 400 holes about the patternsformed with a hole dimeter of 17 nm in the same wafer was regarded aspopulation.

The results are shown in Table 2. The numerical value in the tablerepresents the standard deviation (nm).

TABLE 2 Resist composition CDU Example 13 Composition 1 2.88 Example 14Composition 2 2.84 Example 15 Composition 6 2.99 Example 16 Composition7 3.12 Example 17 Composition 9 2.91 Example 18 Composition 10 2.98Comparative Example 1 Comparative Composition 1 3.87 Comparative Example2 Comparative Composition 3 4.29 Comparative Example 3 ComparativeComposition 4 3.78

As compared with Comparative Compositions 1, 3 and 4, Compositions 1, 2,6, 7, 9 and 10 exhibited small standard deviation, leading tosatisfactory evaluation of CD uniformity (CDU).

(Evaluation of Exposure of Resist Composition with. Electron Beam: ButylAcetate Development)

Each 6 inch-diameter silicon wafer was treated with hexamethyldisiiazaneon a direct hot plate at 90° C. for 60 seconds. A resist composition wasspin-coated on the silicon wafer in such a manner that the thickness ofthe composition layer became 0.04 μm. The coated silicon wafer wasprebaked on the direct hot plate at the temperature shown in the column.“PB” of Table 1 for 60 seconds to form a composition layer. Using anelectron-beam direct-write system (“ELS-F125 125 keV”, manufactured byELIONIX INC.) , contact hole patterns (hole pitch of 50 nm/hole diameterof 23 nm) were directly written on the composition layer formed on thewafer while changing the exposure dose stepwise.

After the exposure, post-exposure baking was performed on the hot plateat the temperature shown in the column “PEB” of Table 1 for 60 seconds,and then the composition layer on the silicon wafer was developed withbutyl acetate (manufactured by Tokyo Chemical Industry Co., Ltd.) as adeveloping solution at 23° C. for 20 seconds by the dynamic dispensemethod to obtain a resist pattern.

In the resist pattern thus obtained after the exposure, effectivesensitivity was defined as the exposure dose at which a hole diameter of23 nm of the pattern formed was obtained.

<Evaluation of CD Uniformity (CDU)>

In the effective sensitivity, the hole diameter of the pattern formedwith a hole dimeter of 23 nm was determined by measuring 24 times perone hole and the average of the measured values was regarded as theaverage hole diameter. The standard deviation determined under theconditions that the average diameter of 400 holes about the patternsformed with a hole dimeter of 23 nm is the same wafer was regarded aspopulation.

The results are shown in Table 3. The numerical value in the tablerepresents the standard deviation (nm).

TABLE 3 Resist composition CDU Example 19 Composition 3 3.19 Example 20Composition 4 3.08 Example 21 Composition 5 3.01 Example 22 Composition8 3.21 Example 23 Composition 11 3.12 Example 24 Composition 12 3.20Comparative Example 4 Comparative Composition 2 3.38 Comparative Example5 Comparative Composition 3 4.12 Comparative Example 6 ComparativeComposition 4 3.71

As compared with Comparative Compositions 2 to 4, Compositions 3 to 5,8, 11 and 12 exhibited small standard deviation, leading to satisfactoryevaluation of CD uniformity (CDU).

INDUSTRIAL APPLICABILITY

A resin and a resist composition including the same of the presentinvention are suited for fine processing of semiconductors because ofobtaining a resist pattern with satisfactory CD uniformity (CDU), andthus they are industrially very useful.

1. A resin comprising a structural unit represented by formula (a1-5)and a structural unit represented by formula (I):

wherein, in formula (a1-5), R^(a8) represents an alkyl group having 1 to6 carbon atoms which may have a halogen atom, a hydrogen atom or ahalogen atom, Z^(a1) represents a single bond or *—(CH₂)_(h3)—CO-L⁵⁴-,h3 represents an integer of 1 to 4, and * represents a bonding site toL⁵¹, L⁵¹, L⁵², L⁵³ and L⁵⁴ each independently represent —O— or —S—, s1represents an integer of 1 to 3, and s1' represents an integer of 0 to3:

wherein, in formula (I), R¹ represents a hydrogen atom or a methylgroup, A¹ represents a single bond or *—CO—O—, and * represents abonding site to carbon atoms to which —R¹ is bonded, R² represents ahalogen atom, a hydroxy group, a haloalkyl group having 1 to 4 carbonatoms or an alkyl group having 1 to 12 carbon atoms, and —CH₂— includedin the alkyl group may be replaced by —O— or —CO—, mi represents aninteger of 1 to 3, and ni represents an integer of 0 to 4, and when niis 2 or more, a plurality of R² may be the same or different from eachother, in which mi+ni≤5.
 2. The resin according to claim 1, furthercomprising at least one structural unit selected from the groupconsisting of a structural unit represented by formula (a1-1) and astructural unit represented by formula (a1-2):

wherein, in formula (a1-1) and formula (a1-2), L^(a1) and L^(a2) eachindependently represent —O— or *—O—(CH₂)_(k1)—CO—O—, k1 represents aninteger of 1 to 7, and * represents a bonding site to —CO—, R^(a4) andR^(a5) each independently represent a hydrogen atom or a methyl group,R^(a6) and R^(a7) each independently represent an alkyl group having 1to 8 carbon atoms, an alicyclic hydrocarbon group having 3 to 18 carbonatoms, or a group obtained by combining these groups, m1 represents aninteger of 0 to 14, n1 represents an integer of 0 to 10, and n1′represents an integer of 0 to
 3. 3. The resin according to claim 1,further comprising a structural unit represented by formula (a2-A):

wherein, in formula (a2-A), P^(a50) represents a hydrogen atom, ahalogen atom or an alkyl group having 1 to 6 carbon atoms which may havea halogen atom, R^(a51) represents a halogen atom, a hydroxy group, analkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6carbon atoms, an alkylcarbonyl group having 2 to 4 carbon atoms, analkylcarbonyloxy group having 2 to 4 carbon atoms, an acryloyloxy groupor a methacryloyloxy group, A^(a50) represents a single bond or*—X^(a51)-(A^(a52)-X^(a52))_(nb)-, and * represents a bonding site tocarbon atoms to which R^(a50) is bonded, A^(a52) represents analkanediyl group having 1 to 6 carbon atoms, X^(a51) and X^(a52) eachindependently represent —O—, —CO—O— or —O—CO—, nb represents 0 or 1, andmb represents an integer of 0 to 4, and when mb is an integer of 2 ormore, a plurality of R^(a51) may be the same or different from eachother.
 4. The resin according to claim 1, wherein A¹ is a single bond.5. A resist composition comprising the resin according to claim 1 and anacid generator.
 6. The resist composition according to claim 5, whereinthe acid generator comprises a salt represented by formula (B1):

wherein, in formula (B1), Q^(b1) and Q^(b2) each independently representa fluorine atom or a perfluoroalkyl group having 1 to 6 carbon atoms,L^(b1) represents a divalent saturated hydrocarbon group having 1 to 24carbon atoms, —CH₂— included in the divalent saturated hydrocarbon groupmay be replaced by —O— or —CO—, and a hydrogen atom included in thedivalent saturated hydrocarbon group may be substituted with a fluorineatom or a hydroxy group, Y represents a methyl group which may have asubstituent or an alicyclic hydrocarbon group having 3 to 18 carbonatoms which may have a substituent, and —CH₂— included in the alicyclichydrocarbon group may be replaced by —O—, —S(O)₂— or —CO—, and Z⁺ ifrepresents an organic cation.
 7. The resist composition according toclaim 5, further comprising a salt generating an acid having an aciditylower than that of an acid generated from the acid generator.
 8. Amethod for producing a resist pattern, which comprises: (1) a step ofapplying the resist composition according to claim 5 on a substrate, (2)a step of drying the applied composition to form a composition layer,(3) a step of exposing the composition layer, (4) a step of heating theexposed composition layer, and (5) a step of developing the heatedcomposition layer.